I don’t disagree, but if it’s a case where the janky file problem ONLY appears in Jellyfin but not Plex, then, well, jank or not, that’s still Jellyfin doing something weird.
No reason why Jellyfin would decide the French audio track should be played every 3rd episode, or that it should just pick a random subtitle track when Plex isn’t doing it on exactly the same files.
I agree but also say that learning enough to be able to write simple bash scripts is maybe required.
There’s always going to be stuff you want to automate and knowing enough bash to bang out a script that does what you want that you can drop into cron or systemd timers is probably a useful time investment.