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)
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: In the saloon, Mad Dog shoots at Marty, forcing him to dance. Marty goes into his moon walk dance, and just before he launches the spit jug at Mad Dog, he does a jump. Watch as he lands - the jug is suddenly 4 to 6 feet to the right of him.
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)
Continuity mistake: Just after Doc saves Clara from the ravine, the carriage flips on its side and rolls. In the next shot, it's stopped rolling and is falling neatly straight down. (00:41:30)
Continuity mistake: While Marty is outside the mine, the sun changes on the floor.
Continuity mistake: While Doc saves Marty from Biff the sun changes between shots.
Revealing mistake: When Buford is about to duel Marty, the back shots of Doc show his hair short, as opposed to the front shots, revealing it's a stand-in.
Deliberate mistake: In the duel with Marty, when Tannen gets fancy spinning his gun, when he places it in the holster the grip is facing forward. They then use effects to turn the gun so the grip is facing back. (01:26:44)
Suggested correction: No, the gun is spinning on his finger and goes into the holster with the grip facing towards the back, which is completely consistent with the spin of the gun.
Revealing mistake: When Doc jumps from the horse to the train, right after he hurries Marty, the man on the horse is an obvious stunt double for Michael J. Fox.
Continuity mistake: When Marty holds the temperature-meter and warns Doc to put the yellow log inside the firebox, his finger suddenly disappears between shots.
Continuity mistake: When Buford hangs Marty, he puts the rope around his neck once. In the close-up the rope goes around twice.
Continuity mistake: When Marty and Buford duel, Seamus' distance to the bartender keeps increasing / decreasing randomly between shots.
Continuity mistake: When the train hits 70 mph the chimney explodes to pieces. When the bar that Clara holds onto breaks the chimney reappears.
Revealing mistake: When the train pushes the DeLorean and hits 70 mph Doc tries to grab Clara. In the wide shots (where we can't see his face) his coat whips, but in the close-ups where we do see his face the coat flutters, revealing that the train was going much faster with the stuntman.
Continuity mistake: After the festival, Marty wakes up and grabs the gun belt, which is missing a bullet. When he mimics in front of the mirror the bullet has magically appeared.
Continuity mistake: When Doc holds the telescope and tells Clara that he'll fix it, right when they date at the festival the position of the telescope changes between the front and back shots.
Continuity mistake: After Clara pulls the emergency pull cord she jumps out of the train with her gloves on. From the immediate opposite angle her hands are bare.
Continuity mistake: When Marty is about to duel against Buford he is inside a house peeping through the window, pulling the curtain open. The position of his hand and the opening of the curtain differs between shots.
Continuity mistake: Buford spills the spittoon on his shirt, but when he lassos Marty his shirt is dry and clean.
