Thanks to @Shadow@lemmy.ca and @Lem453@lemmy.ca Windows event viewer put me on the right path. The errors were coming from the .net installation. Which reminded me that I had recently uninstalled visual studio, and that jellyfin uses .net. Rerunning the jellyfin installer fixed the .net issue and I am up and running again.
while enabling the subtitle burn-in for all complex formats helped… the subtitles show up a little early. And instead of just forced, it shows them all the time. It also didn’t totally solve the problem. Seems like the issue is triggered at the transition points where forced subtitles would start or stop. The playback jumps to some others spot in the show, and the subtitles end up being from a totally difference scene. :(