If I enable the option to play a cinema trailer before a movie it causes pre-roll and the movie file to be transcoded while playing - unchecking the boxes in the Extras section fixes it.
It seems that when a cinema trailer is streamed from the internet Plex transcodes it but fails to realise that it can play both the pre-roll and the movie file directly and continues to transcode everything causing the movie to buffer intermittently unless you stop the movie a few minutes in, manually change the video playback from Auto to Direct Play and resume the movie.
Not a huge issue - I’ve just unchecked the 3 “Include Cinema Trailers” options and will just do without them until it’s fixed
