Plex stuck on creating thumbnails (FFmpeg issue)

AFAIK it’s just -skip_frame nokey that fails in that case.

Well, yeah, that’s exactly what’s happening here.

Does your original have the encoding settings embedded? Can you share the stuff Chuck asked for, a bigger sample of the file, and/or the output from mediainfo ?

I didn’t really wanna invest too much time in debugging this because I know Plex doesn’t really care about these kinds of issues (don’t get me wrong, it’s still a great product). So anyway, turns out that it’s a mixture between having open GOPs (open_gop=1) and setting the GOP length too low (keyint<=25).
Same thing happend in the other post (open_gop=1:keyint=24).