Audio problem: After Doc and Marty return to 1955 in an effort to steal the almanac back from Biff, they land the DeLorean. Doc says, "Here's some binoculars" then says "and" but watch his lips as he says "and", it just doesn't match. You could argue that it is a bad angle but even at the angle it's at, you get an OK view. (01:03:05)
Audio problem: When old and young Biff listen to the end of the football game in the car, as the two are talking back and forth about how old Biff knew what the results would be, the sound of the announcer on the radio lowers and then suddenly disappears altogether... yet neither of them physically turn the radio down or off. The two are shown the whole time talking to each other and both their hands are away from the radio.
Audio problem: When Marty follows Biff into the dance hall trying to get the sports almanac, right after he uses his binoculars he exits the dance hall. If you listen carefully to the music, the music plays uninterrupted, when given the jump in scene it should skip to a further point in the song.