Hey mate, no useful logs but I get go scorched earth since this post as it was just annoying me.
I've been running the same unRaid for years so just got a new USB / Fresh Install / New Docker setup (using existing cache data).
Everything has been running perfectly from Plex since then, sure only 30 hours now but that's much better than it was under Plex Docker.
I'm assuming the over the course of multiple years / upgrades something gets a little skewed along the way.