BTW I checked the history, the only difference in the profiles is in the ffmpeg-general section
instead of -async 1 -thread 0
It's reverse
-thread 0 -async 1
see if that makes a difference.
Otherwise it's FFMPEG (there's a new version here but it may have broken something with mpeg4, you'll need to upload the file along with your log file to debug this further if nothing works)