Factual error: At the end of the film Rainwood has established his innocence of the drug charges and is happily back at work as a senior mechanic for a large airline. However, part of the sentencing and plea bargain protocols at his arraignment is his previous conviction on a lesser drug charge years before. It goes without saying that he did not advise his employers of this when he started work for them - no airline in the world (even pre 9/11) would hire someone with a drug conviction on their record! Now this is out in the open the airline knows that Rainwood is a convicted drug user (on the lesser, legitimate charge) and that he lied on his original job application. They wouldn't hire him again to sweep the floors.
Continuity mistake: In the library scene Indy discovers the "X" high up on the balcony. The X is green with a grey background. When he breaks the tile to find the tomb the X has become a faint outline on the floor. (00:27:40 - 00:28:45)
Plot hole: R.J. Fletcher is shown as a ruthless businessman who knows everything there is to know about Channel 62 - who owns it, how much it's worth, who is running it, the financial troubles it is having and so on and so on. He is also fully aware of the telethon and the fact that George is selling the station as a going concern for a total of $75,000.00. It is simply asking too much of audience credulity or 'suspension of belief' to think that such a hard-headed businessman would not work out that he could, using stooges, buy a controlling interest in the station for $37,501.00, saving himself a small fortune and closing the station down over the objections of his minority shareholders. Something this blatant could not possibly be a character mistake - he is already planning on buying the station for the full price (from Big Louis) so don't tell me he wouldn't just switch plans and buy it from George instead!
Continuity mistake: The batting order in the one-game playoff is Taylor-Dorn-Cerrano (as seen in the 7th), with Hayes batting before Taylor (as seen in the 9th). Cerrano hits the homer with two outs in the 7th, and Hayes is shown batting with nobody on, and two outs in the 9th. If they faced the minimum, Hayes would've been up with only one out (#5 batter gets the third out in the 7th, 6-7-8 batters get out in the 8th, and the #9 batter gets one out before Hayes). There's no way they could've gone through the line-up again without scoring a run. The furthest they could've gotten was the #8 batter (two spots before the leadoff Hayes) coming to bat in the 9th with two outs and nobody on. (01:23:30)
Factual error: The film takes place in a private boarding school the 1950's, however one of the students is studying from a 1980's chemistry textbook. The obvious giveaway is that the spine of one book shows HBJ as the publisher. Jovanovich was not added to Harcourt Brace until the 1970s.
Revealing mistake: When the 54th Mass. marches past a liberated plantation some black children wave them on. One of them is wearing a digital wristwatch.
Continuity mistake: Notice Marty's hair in the scene when he's playing "Johnny B. Goode." It's quite larger than when he says, some seconds later, "I guess that you're not ready for it yet." That's because when he says that, it's a recycled shot from the original BTTF, whereas most shots showing he's playing the guitar are newly made for BTTF2. However, Marty's hair is considerably longer in the new shots.
Audio problem: In the scene where Leo explains how he launders the drug money and Roger says "You're a cheat", Leo says "Come on, everyone cheats a little, look at the pentagon." But when he says "look at the pentagon", it's dubbed in because the sound of his voice doesn't match his other dialogue, and if you read his lips it doesn't match either.
Continuity mistake: During the first car ride scene Harry is spitting the seeds out the window. One of the shots shown of the car from the outside shows the window still up after he has rolled it down.
Continuity mistake: In the scene where Ouiser sits and lets out a belch, if you look in the mirror, you can catch her laughing.
Continuity mistake: Early in the film Bud throws his wedding ring down the latrine and then retrieves it with his right hand so it is covered with the blue disinfectant. In a (much) later scene, Bud has a blue right hand, despite not having had one in the intervening period. (01:44:48)