Recently I started experiencing Plex playback issues on my XBox One. As it turned out, I inadvertently (ignorantly) changed the Plex App’s Video => Maximum H.264 Level setting to 5.1.
FYI, the Plex app on XBox One only supports H.264 Level 4.0 and below, as documented here:
https://support.plex.tv/articles/203810286-what-media-formats-are-supported/
After I changed the setting to 4.0, all my videos encoded at >4.0 started playing again, my Plex server transcoding them in real time!
