Continuity mistake: When Marty sees his dad punch Biff, he sees his other self standing near the group of people. He pushes between a guy and his date with nobody behind them. In the first film, there are more people behind them that Marty had to push through.
Continuity mistake: When Doc and Marty arrive in 2015's Hill Valley the flying DeLorean (a scale model) is missing the key lock and door handle dent. When it lands (and swaps to a real car) both appear.
Revealing mistake: When the movie begins and the car takes off (achieved with a scale model car) note Doc's stiffness and fuzzy hair, revealing he was replaced by a dummy.
Continuity mistake: 1955-Jen is showing some dresses to a friend when Biff shows up. Watch the man passing by the girls. He walks by twice.
Continuity mistake: Inside the tunnel, Biff punches Marty who's on the hoverboard, launching him back. A shot later Marty is suddenly standing tall and next to Biff, and gets punched again.
Continuity mistake: When 1955-Marty reads Doc's 1885 letter next to the Western Union car, his right hand is either on the lower part of the paper or the upper, depending on the shot.
Continuity mistake: When 1985-Jen encounters her old self, 2015-Jen walks several steps further. When the angle changes, old-Jen has stepped back 4 meters to allow for both to stare at each other closely.
Continuity mistake: When Jen finds out that she got married in the chapel of love, her hair swaps from perfectly brushed to totally messed-up between shots.
Revealing mistake: Doc and Marty hide in the alleyway while the flying police car takes 1985-Jen home. Problem is, Doc stares in awe at the sky before the police car is in view.
Continuity mistake: After Jen is taken to her home in the future, Marty and Doc are in the car. Doc places his left hand over his glasses, but when the shot changes he's got his pinky finger raised.
Other mistake: Griff enters Cafe 80s and tells Grandpa to wax the car. Grandpa stands up and walks to the door, but Griff keeps looking at where he was standing before. This was due to the VistaGlide system of filming an empty space without stunts that could serve as cues as to where to look at.
Continuity mistake: At the beginning of the movie when Doc smashes through the trash cans, his glasses are not on. In the shot where he steps out of the car they are.
Suggested correction: He put them on in between shots.
Continuity mistake: During the beginning of the chase sequence, Marty is hanging on to a rope and there is a rear facing shot looking at him. There are two wet tire tracks in the shot. These disappear in the following shots.
Continuity mistake: When Marty is on Strickland's porch with the shotgun pointed at him, his hands go from in the air to down by his waist in a split second.
Continuity mistake: Int the courtyard chase scene when Griff and gang crash through the courthouse windows, the sun's position changes in every shot.
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.
Continuity mistake: When Strickland is hitting Biff with the Almanac in the parking lot, the way the book is folded changes between shots.
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.
