The problem with an Unknown Error is that the cause is...unknown. Without knowing the cause, it can be difficult to find a solution.
Having said that, I've noticed this issue on one sequence using two pass. Try just one pass.
Well it seems to only happen when I have the AAC audio compression selected, if I use another codec or uncompressed the export is fine.
Apologies for my ignorance. I'm exporting as a Quicktime file, H.264 25P, I can't see an option to specify the number of passes.
Is there one for an H264 export?
I'm exporting as a Quicktime file
Ah. That's the one you want to change. Use the normal MP4 container.
MPEG4 'Match sequence settings' works great, however I'm pretty sure that it uses an uncompressed audio format.
It seems that there is a bug when exporting as H264 with AAC.
Thanks for you help!
AAC is the only option for an MP4 file.