Unfortunately Plex have long lost interest in this issue and as @City-Cobra states its almost certainly an issue in the updated ExoPlayer which Plex have no control over. In short it wont be fixed and we all have to stay on 9.28 until such time as a Plex server update kills its functionality. I see some big changes coming to the Plex client app soon but hopefully this wont mean 9.28 is made unusable.
Also @johnajohnsen would you report your success with the roll back in this other thread please? Its annoying its covered in two threads but some wont see both.
