Since no one has replied, I’ll wade in. Have you tried some standard troubleshooting things?
Delete the app from the Roku and re-add it?
Load the Preview app also and see if it does the same thing? (Look for a link to the preview channel in this thread):
Try turning on subtitles to force Plex to transcode it.
You also might want to take a screenshot of the Dashboard while it’s playing. Might give some other clues.
Good luck!
