Feature lenghth (90 min) prores to .mp4 is only 1kb in size.
Does this happen every time for this file? How many audio channels does the source have? A H.264 file can only support up to 8 channels. I suggest not using passthrough audio and see if that helps.
Yes, this happens every time. 2ch audio file. Using audio mix 1-1 / 2-2 didn’t help.