When applying "reverse speed" on a clip in the timeline, picture breaks apart during playback but also on the exported timeline using Media Encoder. See attached sample. The clip of the kid on the horse holding the reins is set to "reverse".
Actually, keep it open. I am having the issue again. It sounds like applying "reverse" effect on a clip in the timeline can lead to corruption and cause playback issue on that clip. Investigating... Media is 4K 24.98P, XAVC-L in a 1080 23.98P timeline.
@Bruce Bullis see below link to the source media for the clip that has reversed applied in the sequence and causing playback problem. Also included copy of the project. There is only one timeline in the project TIMELINES bin called TEST Timeline. The clip is inserted between 44:23 and 51:18. Good luck!
[I received the files, so removed the download link from public view]
@Bruce Bullis I did a few quick tests. Within the project, created an empty timeline and just pasted in the problematic clip. Applied reverse and could reproduce the playback issue. So, it doesn't seem affected by anything around the clip in the sequence.
For testing purposes, could you please try disabling hardware accelerated decoding under Premiere Pro > Settings > Media and check if it fixes the preview? Please note that you would need to restart Premiere Pro after disabling hardware accelerated decoding in Settings.