I'm expecting the same issue. FYI, I don't have a single droppped frame but my audio ans video is out of sync, even if I record the audio from my sound card mic.
It's easy to see when I am converting a VHS of 3 hours, at the beginning (0 to ~1hour) everything is ok, then the audio is slightly not in time and it's getting worst and worst.
Is there any way to fix it ?