Thanks a lot for this Shebun! This is a bug that we found ourselves some weeks ago. It can even crash AP when exporting in some cases. Sorry about that. We will have it fixed for the next release for sure.
Did you try exporting as MOV? This should work with sound and actually it is the higher quality format that Youtube will accept as well (the file is larger though, so it will require longer upload time – I hope that is fine).