Server Version#: 1.28.2.6106
Player Version#: 2.05
Using Debian 11 on my Plex server and have 1 gig symmetrical service.
A friend was streaming the 4K version of ‘No Time to Die’ from me on his PS4 (it was hardwired). When the subtitles are off, it plays perfectly. As soon as he turns on subtitles, Plex buffers non-stop.
If you’re using the original blu-ray or DVD subtitles ripped from the disc, the server has to transcode the video if the client is a Playstation, which is tough for a lot of servers at 4k. Try using text subtitles either from a search on Plex or download them yourself.