Audio problem: When Mad-dog Tannen is standing over Marty, who is playing possum, you see Tannen cock his gun twice between two shots, although there is no sound effect for the first time. (01:27:50)
Continuity mistake: When Doc and Marty are chasing the train, first their shadow is on the left of them, then in the next shot it's on the right. (01:30:40)
Continuity mistake: When Doc and Marty are chasing the train on horseback, Doc gets on the train first and his horse pulls forward. Then when the camera shows Marty on his horse, another horse can be seen in front of him. When Marty jumps on the train, his horse falls back. But in the next shot you can still see the horse as it moves off camera. (01:30:55)
Continuity mistake: When Doc and Marty get on the train at the end, Marty has some trouble getting on, and note that his hat falls off in the sequence, but in the next shot when Doc and Marty fall the hat is back on. (01:31:15)
Continuity mistake: When Clara first sees the train and starts after it on horseback, it is on her right side. She is at the top of a hill and starts down after the train. In the next shot shown from the front of the train you see the horse appear so the train is on Clara's left. (01:34:09)
Factual error: Each time one of the special Presto-logs begins to burn the locomotive suddenly accelerates. In real life the logs would heat the water faster and generate more steam, but there would be an appreciable time-lag between the time the logs begin to burn and the engine accelerates. Also, train engines must accelerate slowly. If too much power is applied the drive wheels merely spin on the rails. (01:35:20)
Deliberate mistake: During the train sequence at the end of the film in 1885, it is blatantly obvious that the train is not going the speed that the DeLorean's speedometer is showing. In some shots, the train looks as though it is going little more than 20mph. (01:38:55)
Continuity mistake: When the train hits 70 mph the chimney explodes to pieces. When the bar that Clara holds onto breaks the chimney reappears. (01:39:53)
Factual error: When the red Presto-log is burning, rivets begin to blow out of the locomotive, supposedly from the pressure. The rivets in the boiler, which would be subjected to pressure, are not visible on the outside of a locomotive. The rivets which are seen to blow out in the movie are in the smokebox, an area which is subjected to heat and smoke, but no steam pressure. (01:40:10)
Factual error: At the end of the train scene just before Marty travels to 1985, the train busts through a road block warning that there's only 1/4 mile of track left before the ravine. Keep in mind that the train is travelling at approximately 70-80 mph by this time. At 70 mph (and not even accelerating) it would only take the train 13 seconds to reach the ravine. The actual time in the movie is at least a minute. (01:40:31)
Suggested correction: This can't really be classed as a factual error because we don't know how much of the track has been built since that barrier was put up. They could've put that barrier up when there was only 440 yards or so of track left, but have laid another 800 yards of track since then. I myself actually work on the roads; if we're resurfacing a road, we don't move the sign 100 yards further up the road every time we've resurfaced 100 yards. That sign stays there till we're done, regardless of the distance.
Continuity mistake: After the train crashes against the "Tracks end" sign, the editing is all wrong: Marty is inside the car covering his head with the hover board. Half a second later he has magically moved outside the car, dangling and holding the hover board. Then we see Clara upside down, and back to Marty back inside, removing the hover board from his head after the crash. then he dangles outside with the hover board. So the first shot of him dangling shouldn't have been there. (01:40:42)
Revealing mistake: When Clara's dress rips off and is about to fall off the train, Doc saves her. One can notice it's not Christopher Lloyd but his stunt double. (01:41:17)
Continuity mistake: When the railroad is about to end, Marty puts on his hat and there's a POV shot where we see the train passing by some abandoned tracks on the grass to the left. Then a wide angle shows some explosions going on and the train passing by the same place again. (01:41:37)
Continuity mistake: In the scene where Marty is driving the black Toyota pickup at the end of the movie, the truck's registration plate is missing - it can be seen when the truck is in the garage at the start of the film. Also the driver's door quarter light (vent window) is open. When we see the inside of the door it is closed. (01:41:45)
Revealing mistake: In the overhead shot of the train explosion, you can tell which explosion is 'real' and which one is fake - the second explosion appears out of nowhere from the first one. (01:42:00)
Continuity mistake: When the train is coming and is about to run over the DeLorean, the shadow of the train on the wall shows that it is only the locomotive. When the camera changes view, it is a train with freight carriages. (01:43:00)
Revealing mistake: At the end, when the train destroys the time machine, right at the moment when it hits you can see a small explosion, which was used to trigger the destruction of the time machine. (01:43:03)
Continuity mistake: In the last fifteen minutes of the film Marty wears his Wild West clothes, including his brown woolen poncho. The front of the poncho is unmarked, completely intact. Shouldn't it have a bullet hole in it? (01:43:50)
Revealing mistake: After the train destroys the DeLorean, its vanity plate is shown spinning around. Just like in the first film, the plate is attached to a steel post stuck into a hole in the train track, which is visible. (01:43:50)
Continuity mistake: When Marty returns to 1985, he goes to his house and gets in his Toyota pick-up. Look closely behind his head when he first gets in the truck, there is no driver-side head rest. But when he picks up Jennifer, when they pull up to the stop sign the head rest is there. (01:45:00)
