Plex on ipadOS 15 won't play a number of videos, some others play with no sound, some play just fine

[FordGuy61]

Known issue.

Playing videos with Stereo MP3 has no Audio in tvOS 15 beta

Also happening with other audio formats. There are multiple threads on the topic. iPhones/iPads are exhibiting similar issues with iOS 15 beta. Second thread below mentions a possible workaround, forcing a transcode.