Continuity mistake: Marty's hairstyle is different in the starting scene in BTTF2 to what it was in the scene at the end of BTTF (It is flatter).
Continuity mistake: When Marty gets locked in Biff's garage, we see that he can't push through the two garage doors because there's a lock on the other side. Yet, when Biff comes out to go to the Prom dance, he opens them in literally no time at all with no resistance. We don't even hear him unlock them.
Visible crew/equipment: Just as Griff is about to crash through the front door of the court house after he is chasing Marty on the hover board, you can see someone (the director?) on some sort of crane in the reflection of the glass. (00:20:58)
Continuity mistake: When Old Biff is seen watching the hover board chase all the monitors on the wall in the Cafe 80's are turned off even though they were all on two shots prior.
Continuity mistake: When Griff pulls "Gramps" Biff out of the cafe 80's, as he swings back into the cafe notice that he swings around twice. (00:15:00)
Continuity mistake: When Biff is trying to run down Marty on the hoverboard, as he comes out of the tunnel there is a shot of the manure truck driving down the road. Cut camera angle to Biff missing Marty and hitting the truck, which is now at a dead stop, however there was not adequate time to do this and appears that the truck was driving then instantly stopped.
Continuity mistake: The small black pickup Marty is given at the start of this film is significantly different from the one he's given at the end of the first movie. Yet the moment is supposed to be the same one.
Continuity mistake: When Marty is waiting for Griff he orders a Pepsi and has trouble opening it, but at another angle it's out of his hands and on the table, then in the next shot he's trying to open it again. (00:13:41)
Continuity mistake: In the tunnel chase, watch the next shot after Biff laughs which shows Marty furiously using all his might to escape Biff. There is suddenly black on the walls around where Marty is.
Plot hole: When Old Biff goes back to 1955 to give himself the almanac, he comes back in the Delorean to the version of 2015 that he left, not the other, skewed version in which he is rich. Everything in 1955 should have changed around the Doc and Marty, as the Doc tells Marty everything will change around Jennifer and Einstein later on in 1985, when Marty and the Doc go back to restore normalcy. George is alive in this future, so we know the skewed version hasn't taken hold.
Suggested correction: It is established in the movies that the effects of the timeline being changed are not immediate. For example, in the first movie, in the photo of Marty and his siblings, it takes some time for them to vanish from it. When Doc tells Marty everything will change around Jennifer and Einstein when the timeline is restored, I don't think he meant the future will be restored to normalcy right that second, but more after an ample amount of time has passed for everything to be right. After Old Biff gave the almanac to young Biff, there was ample time for him to return to the original 2015 before it changed into the alternate 2015.
That would mean when they restored the timelines it would have taken time for it to adjust again, but it didn't. The new timeline was created but the old one remained because Marty and Doc were still in the original future. However, even though they are not in their original timeline it doesn't make sense for them to still be there, the timeline should have been erased or else old Biff wouldn't be erased either. Again though, a copy of another plot hole, which one is the oldest and original?
Continuity mistake: When Marvin, the band member, goes to call Chuck Berry about Marty's "new sound", the telephone he uses has a black neoprene coiled handset cord. In the first BTTF, the phone had a straight, uncoiled brown cloth handset cord (seen when he says, "Well then listen to this." and holds the handset out toward the stage). This isn't because the cord was stretched out, as neoprene cords can't stretch so much that they look uncoiled.
Continuity mistake: At the start, the DeLorean hits the left dustbin and comes to a halt. At the other side of the street, there is only one car parking near to a house. From another angle there's a different red car parking on the other side of the street, and the tree that stood between both houses has gone. (00:01:15)
Continuity mistake: When Doc drives Marty up behind Biff, just before they enter the tunnel and Marty grabs Biff's car, you see Doc acknowledge Marty and then turn off left, but as the camera pans back you see the car veer to the right. (01:30:45)
Continuity mistake: When Marty is at the dance in the first film, the room that the band leader rings his cousin from is on the right, but in this film the room is on the left. (01:26:09)
Continuity mistake: When the rain stops after Marty and Doc first get out of the DeLorean in 2015, Doc looks up at the rapidly clearing sky. Directly above their heads the sun is shining brightly. However, if you look at the tops of the buildings you can see sunlight hitting them from the sides. I suppose we will have another sun by 2015? (00:06:42)
Continuity mistake: In the Café 80's, when Griff is about to bat Marty, a woman in a blue dress passes behind Marty twice. She is also seen walking around in the next scenes that take place outside.
Revealing mistake: During the tunnel chase at the end of the movie, in the shot shown from the ceiling of the tunnel, you can see in the shadow of the hover-board, skate-board wheels.
Continuity mistake: When Marty is in the Café 80's, there are two men talking outside on the street. Shot changes and when we go back to Marty, a second later, the two men have vanished.
Continuity mistake: When Marty is going over the lake on the hover board, at the start his shoes go right under the water, but if you look at his shoes in the next shot, they are dry.
Visible crew/equipment: When Doc, Marty and Jennifer are going to leave 1985 (at the beginning of the movie), the camera is reflected in the back part of the car.
