I'm running Plex version 18.104.22.16817 (I know, it's old) on my FreeNAS server and I have a problem where if I pause a show for a long enough period of time, then if I try to play it it will play for a minute or two and then begin to buffer indefinitely. If I leave the video and click back into it and choose "play from time xx:xx", then it will also just buffer indefinitely. The only way to get the video to play is to start it from the beginning. Also, if I let it auto-play, after two or three episodes I run into the same buffering problem and have to quit and play the next episode from the beginning. And if I try to skip ahead in a video, then it will also buffer indefinitely. I never used to have this issue, but I do now and I'm not sure what's causing it. I plan on updating when I get a chance, but I'm not able to access the server easily at the moment and so I'm not willing to update it until I can have access.
P.s. when I say buffer indefinitely, I don't mean it will play for a second and then pause to buffer and then play again. It will just sit paused and buffer forever but never actually be able to play.