Other mistake: When Miyagi throws Mike into the light switches, the lights go out but the switches never change position.
Other mistake: When Doc, Marty and Jennifer have arrived in 2015 Doc tells them that the time of the day is 4:29pm. However the destination time is still shown on the time circuits' display from their time travel to the future - the two times should match, but the destination time has the bottom AM/PM light illuminated, while the current time has the top one lit. They didn't arrive or leave at 4:29am, so something's wrong somewhere. (00:04:42)
Other mistake: When Ariel is at the dinner table with Eric and Grimsby, Ariel takes Grimsby's pipe and blows it in his face, yet when he wipes his face there isn't any black stuff on his hankie.
Other mistake: When Nick is in the spoon, the milk around him turns green.
Other mistake: At the bus station Hayley manages to score 25250 at Double Dragon. Jimmy needs to beat this score so Corey gets his $6.70. During the Double Dragon montage of Jimmy playing trying to beat Hayley's score, the first footage we see of the score, its already at 27850. Strangely Corey waits till Jimmy is at 29920 until he's satisfied that Hayley's score is beaten and he snatches her money from her hands.
Other mistake: Moonlight Graham is hitchhiking; Ray stops to pick him up. The kid talks at the window; Ray says to get in, and he opens the door to get in. No way a kid from the 1920s would know how to open a Volkswagen side sliding door.