Related but would need to see the full log to know:
This happened after after FFmpeg upgrade after v20.07.11, but it was fixed for some in versions 20.10 and 20.11 by downgrading it back to what was in v20.07.11
The full log is at View > Application Log… no need to go hunting for files unless you want to get the log after a crash because it resets when the app starts.