VideoVariableFrameRateNotSupported (Video track used a variable frame rate. Only constant frame rates are permitted)
Multiple entries in 'stts' box not currently supported. This usually indicates a variable frame rate or a fragmented file
The video asset uses a non-constant frame rate, which is not supported. Video assets are required to use a constant frame rate (e.g. 23.976fps) throughout their entire runtime.
A variable framerate cannot be undone. Attempting to re-transcode a file with a variable framerate into a constant framerate can result in poor-quality playback. You will need to seek an alternate source to use for delivery.