I have some stuttering and looping on local playback on same machine as server.
I have a 7950x3d system, a 14tb hdd. If I watch a movie with a friend or by myself I get basically a loop on playback happen, it will loop maybe 5 seconds of the film like 10 times or so on chrome or edge, where as my friend remotely connected playback is fine? I’m not sure whats causing this i have tried hardware playback on and off in chrome etc to no avail, and reinstalled the server. I can’t see what it is, my use is very low as obviously its a capable cpu. Windows 11 if it helps.
See if the situation improves if you use “Plex for Windows” instead of a web browser for playback.
Download link below.
(You might have to reduce the “Playback quality” setting in the preferences of this player. It applies by default a very elaborate post-processing to the picture, which causes a hefty load on the whole system. )
Absolutely fixed it!
Thank-You Sir 
