One of my git repositories can't be archived or fetched

[ORBAT]

Describe the bug
Trying to fetch or archive one of my repositories always results in Server: block does not exist, and archiving gets stuck in the indexing phase.

my log id: 1056df53707dbcf41442ea1c

Additional numbers
The number 345567

[ORBAT]

Whoops, realised I'd already reported essentially the same bug way back in 2018: #11358