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: 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. (01:09:39)
Audio problem: As Marty and the sales guy are watching the sports flash thing, Marty makes a comment about the Cubs winning against Miami, and when the sales guy says, "Yeah really something isn't it? Who woulda thought," his lips don't match what he says.
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.
Audio problem: When Marty is watching himself talk to Lorraine after playing Johnny B. Goode, you can see and hear Lorraine, "I hope you don't mind but George asked me if he could take me home" but watch her lips and listen. It's way out of sync.
Answer: At the end of the first film, Doc says, "what the hell" in response to the letter Marty gave him. So this shows it is not that strong a conviction, especially in the face of definite knowledge about something bad happening. It is also a way for Doc to repay Marty.
MasterOfAll