Audio problem: When Ariel's sisters are singing in the beginning of the movie the yellowish sister's mouth doesn't move when she says her name.
Audio problem: When Doc and Marty return to the year 1955, you hear the squealing sound of tyres braking heavily, but the DeLorean is flying. (01:02:25)
Audio problem: When Russ jumps from out behind the bush and says, "I say that ant is ours", his mouth doesn't move.
Audio problem: At the Video Armageddon shortly after the event host first realises Jimmy isn't there, the female voice counting down the time proclaims "...the Video Armageddon will commence in T-Minus two minutes and counting". However, the digital timer on the stage is at precisely 01:00, not 02:00. (01:21:15)