Hi there,
Maybe this is a dumb question, but do you have accesss to the video in question? In addition, maybe try "78cao00034" where you pad in extra zeros?
If you look at the Content ID, you can see they usually pad numbers with 00 zeroes to make the number portion a length of 5 places. But this isn't a standard and they sometimes do this internally or sometimes not. It only happens on a small number of titles I think, so hopefully it isn't much of an issue.