[BUG] MMU3 filament change halting a print

[CappyT]

Printer model

Core One

Firmware version

6.3.5-alpha+10514

Upgrades and modifications

MMU3 Enclosed kit

Printing from...

Prusa connect (usb inserted)

Describe the bug

The printer stucks in the loading filament screen (like when you load filaments on mmu) and doesn't do anything else, failing the current print.

How to reproduce

• Run a print
• Make the mmu3 finish the filament mid print
• Make it so that the mmu cannot unload the filament properly, causing an error on the screen (i think it tries 3 times before showing)
• Now "fix" the issue and let filament unload
• Load new filament
• The loading filament screen doesn't go away.

Expected behavior

Filament loads and proceeds to resume printing

Files

N/A

[thomasloven]

What is likely the same bug is still present in 6.4.0 alpha.

MK3.9S with MMU3
Firmware: 6.4.0-alpha+11774
MMU Firmware: 3.0.3

I find the printer in the parked position with "Reloading Filament" at 100 % and "Parking" showing on the screen.
The filament is not unloaded from the hotend and the printer does not react to any button presses except reset.

I have not been monitoring the printer, but I assume this happens when a filament swap fails and it is parking waiting for user resolution.

[markaabo]

What is likely the same bug is still present in 6.4.0 alpha.

MK3.9S with MMU3 Firmware: 6.4.0-alpha+11774 MMU Firmware: 3.0.3

I find the printer in the parked position with "Reloading Filament" at 100 % and "Parking" showing on the screen. The filament is not unloaded from the hotend and the printer does not react to any button presses except reset.

I have not been monitoring the printer, but I assume this happens when a filament swap fails and it is parking waiting for user resolution.

I also have this issue, for me it just gets stuck at 100% without trying to unload the filament, i have not heard the mmu3 make the "pulling" sound when doing it (aka the stepper), so it seems to happen before it actually starts swaping, for me it mostly happens on my number 5 filament but that is always my support filament which is used the most so could be just by chance. but just wanted to add it as a note.

[JGeiger2024]

I am having similar issues with MK4S + MMU3 + 6.4.0 Alpha. Mine is slightly different in that it always gets stuck at 99% Parking.
It happens after successfully laying down the initial prime line

[drGarbinsky]

I too have this issue on a mk3.9. 6.4.0 final release

[m42e]

Same here, MK4S + 6.4.0 final with an MMU3 it occurs occasionally.

[markaabo]

It literally just happened to my printer, like 5 min before i got the github updated notification. with newest fw and Prusaslicer on MK4S

[m42e]

I restarted the print, The last time I had this issue resetting the EEPROM of the MMU helped, will try that again if it fails this time, too.

https://help.prusa3d.com/article/factory-reset-mmu_510075

FYI:

After getting into this issue two times I resented the MMUs EEPROM and now it run through smoothly (after reloading the filament into the MMU after the reset, as the 'time till finda' has to caused issues at the beginning which is kinda expected)

[m42e]

I am unsure if this helps but i managed to activate syslog before the "crash" happened:

{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MarlinServer","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782541665866824,"message":"E-stall detection off"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782547604758598,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782549605394216,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782551604702348,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782554782882995,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782556783974522,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782558782241744,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782560782242083,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782562782213162,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782564957617418,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782566215504622,"message":"Unloading to FINDA"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782566957948092,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782568957715856,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782569285068982,"message":"Retract from FINDA"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782570957799270,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782572958733149,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782574324458711,"message":"RSTCommTimeout"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782574328162261,"message":"RSTCommTimeout"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782574330464102,"message":"RSTCommTimeout"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782574348463180,"message":"Feeding to extruder"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782576957365990,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782578726170523,"message":"Disengaging idler"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782578957153199,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782579751519898,"message":"ResetRetryAttempts"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782579751927677,"message":"CompensatedFeedDistance=49.1"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782580957206132,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MarlinServer","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782581599693084,"message":"E-stall detection on (restore)"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"GUI","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782581600552069,"message":"get_underlying_screen_state() without screen"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782584672909495,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782586672120221,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782814324332373,"message":"X:80.85 Y:186.23 Z:0.40 E:0.00 Count X:8419 Y:18128 Z:-39"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782821875650358,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782823876518843,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782825876168957,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782829053068532,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782833052593230,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782837052163467,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782839224971143,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782840482980099,"message":"Unloading to FINDA"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782841225041691,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782843225033910,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782843550177041,"message":"Retract from FINDA"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782845593904775,"message":"Feeding to FINDA"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782847225692943,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782847634148606,"message":"Feeding to extruder"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782849224578802,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782850709487834,"message":"Feeding to FSensor"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782851224667469,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782853224527492,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782853299254334,"message":"Disengaging idler"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782854323382044,"message":"ResetRetryAttempts"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MMU2","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782854324503531,"message":"CompensatedFeedDistance=50.0"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782855224305076,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MarlinServer","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782856205188790,"message":"E-stall detection on (restore)"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"GUI","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782856205327550,"message":"get_underlying_screen_state() without screen"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782859354946196,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782866446989969,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782866824469296,"message":"X:45.71 Y:28.70 Z:0.60 E:0.00 Count X:4570 Y:2870 Z:193"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782932680468254,"message":"E-motor stall detected"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MarlinServer","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782933062949883,"message":"ExtUI: onPrintTimerPaused"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MarlinServer","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782934191600043,"message":"setPhase 3 1"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MarlinServer","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782934344013410,"message":"Parking"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"MarlinServer","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782934345456361,"message":"Park done"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782937060271046,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782937679382648,"message":"X:241.00 Y:-3.00 Z:34.97 E:222.52 Count X:24100 Y:-300 Z:13988"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782939063643866,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782941060436956,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782943060036087,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782945060096265,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782947059709522,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782949060016050,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782953059442881,"message":"busy: processing"}
{"level":"info","log_processor":"true","app_name":"buddy","client":"192.168.xxx.xxx","hostname":"MAC-ADDRESS-XXXXX","priority":"14","proc_id":"Marlin","msg_id":"-","severity":"Informational","facility":"1","structured_data":"-","tls_peer":"","version":"1","time":1766782955059371634,"message":"busy: processing"}

[cgspeck]

This hit me today, multiple times.
The first on hour 4 of a 7 hour print.
The second when I attempted to start a print.
This bug has rendered my MK4S + MMU3 unreliable and unusable.
On 6.4.0 final (6.4.0+11974)

[m42e]

Ok, i hope I got it right, but here is what happens according to my analysis:

1. Overview

The message "Reloading filament" appears on the screen when the printer enters the Filament Stuck recovery mode. This is distinct from a standard filament runout or a user-initiated filament change (M600).

2. Trigger Mechanism

The "Reloading filament" state is triggered automatically by the Extruder Motor Stall Detection system. This feature is enabled on printers equipped with a Load Cell.

Sequence of Events:

1. Stall Detection: The EMotorStallDetector inside Marlin.cpp detects a stall on the extruder motor while the axis is moving and pushing filament.
2. G-Code Injection: Upon validating the stall, the firmware injects the internal G-Code M1601.
   • Note: On CoreOne printers, this is currently suppressed/delayed.
3. M1601 Execution: PrusaGcodeSuite::M1601 calls the filament change executor M600_execute.
   • It passes is_filament_stuck = true.
4. Pause FSM Setup: M600_execute calls Pause::filament_change.
   • Ideally, load_type is set to LoadType::filament_stuck (instead of filament_change).

Code Execution Path

Here is the detailed step-by-step execution path from the M600 call to the MMU hang:

1. M1601 / M600 Call:

   • File: src/marlin_stubs/pause/M600.cpp, Line 264
   • Code: Pause::Instance().filament_change(settings, is_filament_stuck);
   • Action: Calls the filament_change method on the singleton Pause instance.

2. Initialization:

   • File: src/marlin_stubs/pause/pause.cpp, Pause::filament_change
   • Logic:
     • Sets load_type to LoadType::filament_stuck (if triggered by M1601) or LoadType::filament_change.
     • Calls invoke_loop() to start the state machine.

3. FSM Loop Start:

   • File: src/marlin_stubs/pause/pause.cpp, Pause::invoke_loop
   • Logic:
     • Calls set(LoadState::start) to initialize the state.
     • Enters a while loop that executes the function pointer corresponding to the current state from the state_handlers array.

4. State: LoadState::start:

   • Handler: Pause::start_process
   • Logic:
     • Switches on load_type.
     • For LoadType::filament_stuck (or filament_change), it calls set(LoadState::unload_start).

5. State: LoadState::unload_start:

   • Handler: Pause::unload_start_process
   • Logic:
     • Checks if (FSensors_instance().HasMMU()).
     • Since an MMU is connected, it enters the if block.
     • Calls set(LoadState::mmu_unload_start).

6. State: LoadState::mmu_unload_start:

   • Handler: Pause::mmu_unload_start_process
   • Action: This is the function where the logic gap exists.

The issue is that Pause::mmu_unload_start_process does NOT handle LoadType::filament_stuck

void Pause::mmu_unload_start_process([[maybe_unused]] Response response) {
    if (load_type == LoadType::unload) {
        // standard unload logic
    } else if (load_type == LoadType::filament_change) {
        // standard M600 logic
    }
    // implicit else: do nothing
    return;
}

Test

I tested it with a custom GCode with the M1601 command and i get the same behaviour. I will try a fix.