Continuity mistake: When Beth and Jam hit heads to pick up his drumstick, she is holding the stick in her right hand. Then next scene, she's rubbing her head with her right hand and holding the stick in her left hand. Then they go back to the original scene and she hands him the drumstick with her right hand.
Revealing mistake: When all four of the guys are driving the Volvo through Detroit, if you watch real close, sometimes you can see 1980's and 90's vehicles parked on the side of the roads. Especially when they show a long shot with an older mustang following them, there is what looks like (it's hard to tell) a newer Buick or Chrysler (like the 300m) on the left side of the screen.
Continuity mistake: The scene where Jam's mom pulls out the K-mart box, at first its a newer K-mart logo, and then when the camera is overhead, its a older logo.
Factual error: The teacher in shop class is reading a newspaper with a headline about the Jim Jones suicide cult in Guyana, saying bodies were found, etc. However, the cult did not take the cyanide Kool-Aid until November 18, 1978, the concert in Detroit takes place October 13, over a month before the Jim Jones suicide/massacre.
Factual error: In the convenience store scene, the kid in the Ace makeup is playing a KISS pinball machine. The movie is set in 1978, so this is impossible, as the KISS pinball machine didn't hit the streets until summer 1979.
Continuity mistake: The slice of pizza on the disco guys' windshield changes from shot to shot. In the close-ups, there are hunks of cheese and drippy sauce splattered all over with crust, yet, in the wide shots the windshield is cleaner, with just a small triangle of crust.
Other mistake: Lex is in the backstage area and is being chased by a guard. He is walking around carrying a piece of drum equipment and he trips over a cord and drops it. But when the camera shot changes back to him the cord is nowhere to be seen, therefore he really tripped over thin air.
Continuity mistake: While the four guys are on their way to Detroit, Trip is hanging out of the sunroof. In the next few shots, you can clearly see that the car has no sunroof for Trip to hang out of. [The Volvo does have a sunroof the whole time, it is actually a moonroof with clean lines that are hard to notice.]