I’m seeing the same, I think its a problem with plex and have logged it here.
I’ve wondered about the length of data, or whether its how busy the PMS is. I’ve found if you stop playback and start again on the same title it sometimes works. Also, there seems to be a better chance of it working if you move through the menus/selections and pause for 5 secs or so, before you start it playing.
My PMS is relatively low powered running on a Netgear NAS, I’ll get round to trying ,y backup server running on windows.
