You may want to look at this first (linked below). I just spotted it, so maybe it could help?
To be honest, as part of my downgrade of PMS, I also made sure to use Nvidia 515 drivers, but wasn’t 100% sure if that helped or not (I just saw a post from another site talking about it).
https://forums.plex.tv/t/latest-update-has-rendered-my-plex-server-un-usable/826455/14
