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.
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.
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.
Visible crew/equipment: During the tunnel chase, after Marty grabs the Almanac Biff speeds up the car. In a close-up of the hubcaps several crewmembers and a man in red are reflected.
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 Doc travels to 1885, Marty stands on the road holding a rope and says "He's gone." When the angle changes, the length of the rope sticking out is much shorter.
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 2015-Lorraine takes the pizza out of the oven, the amount of green peppers decreases between shots.
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: When Marty reads the paper with the news about his son's arrest, the way he holds the paper differs between shots.
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: At the start of the movie Biff is waxing George's car in the driveway with his truck parked next to it. However it completely disappears and isn't seen again even though Doc appears and parks where Biff's truck was, and Biff doesn't leave the premises.
Continuity mistake: Marty's new truck in the garage at the end of Back the the Future I and beginning of Back to the Future II has different front license plates.
