Is Jellyfin or NZBDav to blame for this bizzarre playback problem

[roadhazard]

OS is Debian 13 on bare metal, Jellyfin is bare metal install and nzbdav (0.5.32) is in a Docker

Remote User 1 playback devices are phone and Roku TV
Playing movie A on phone (using web) works
Playing movie A on Roku fails (just a spinning wheel and eventual error and gets dumped back out to the JF app screen
Playing an already fully downloaded movie (B) from the hdd, playback is fine on the phone and JF Roku app

Remote User 2 playback devices are phone and 2nd gen Firestick
Playing movie A on phone (using web) works
Playing movie A on Firestick throws a generic playback error but the app says it's going to retry and seconds later, the movie plays perfectly fine
Playing an already fully downloaded movie (B) from the hdd, playback is fine on the phone and JF Firestick app

Remote User 3 playback devices are phone and Nvidia Shield
Playing movie A on phone (using web) works
Playing movie A on Nvidia Shield fails (just a spinning wheel and eventual error and gets dumped back out to the JF app screen
Playing an already fully downloaded movie (B) from the hdd, playback is fine on the phone and JF Nvidia Shield app

Local User 4 (myself, at my house) playback devices are phone and Nvidia Shield
Playing movie A on phone (using web) works
Playing movie A on Nvidia Shield works
Playing an already fully downloaded movie (B) from the hdd, playback is fine on the phone and JF Nvidia Shield app

Not sure how to interpret these results, none of it adds up. The firewall is opened up else nzbdav wouldn't be able to stream to the phones at remote locations. The Nvidia Shield at my house works fine.....for remote user 3, not so much.

Anyone ever seen something weird like this?