Factual error: This film takes place in 1987, but when Norm Gunderson is talking to Marge about his paintings, he mentions a 29 cent stamp. 29 cent stamps weren't introduced until 1991.
Suggested correction: He mentions "who got" the 29-cents stamp, meaning a person's painting was selected to be on the UPCOMING 29-cents stamp. I don't know if it would take four years to actually manufacture a new stamp with a particular picture (painting), but this "planning" stage would more than likely mean that the 29-cents stamp was not yet (and would not be) available in 1987. Perhaps your entry could be more accurately classified as "other error" instead of "factual"?
Factual error: We learn that the previous sheriff, Charlie Wade, took revenge on anyone who smuggled illegal immigrants across the border in the late 1950s - we are shown the smuggling, as Eladio Cruz hides a group of Mexican men in a watermelon truck to take them across the border. However, in the 1950s, the border was not fortified the way it is now - the smuggling shown would simply not have been necessary.
Factual error: When WD-40 is at the restaurant, the waiter starts talking about himself. He tells the agent he drives a 1969 Ford Pinto, but the Pinto wasn't introduced until 1971.
Factual error: During the song "A Guy Like You," one of the gargoyles trips the trapdoor on Quasimodo's miniature hangman's scaffold. Trapdoors weren't used on scaffolds until the 18th century.
Factual error: The Lee Enfield rifle is chambered by singular repetitions with a bolt action. When Collins' wayward friend is shot in the water, the rifle shots are rapid semi-automatic fire.
Factual error: The Abilene, Texas courthouse should read Taylor County Courthouse, being that Abilene is the county seat of Taylor County, Texas. All Texas courthouses are named by the county they are in.
Factual error: Throughout the movie, we can hear Ash's motorcycle shift gears, but we can see that his hands never disengage the clutch, a must do for a smooth shift like we hear.
Factual error: During the riots and the start of the film a model of armoured car and grenade launcher are seen, which were not manufactured until the 1970's.
Factual error: In a radio news voice-over shortly before the first chase scene, the newsreader comments that "Calls have flooded in from all over the world regarding Dr Barkley's research." He then goes on to mention that the Royal Academy in England has expressed an interest. The "Royal Academy" is more formally the Royal Academy of Arts. They probably mean the Royal Society, which is the most important scientific institution in the UK.
Factual error: When young David and his father show up at Ben Rosen's house, there is a Jewish mezuzah (a handwritten tiny scroll of parchment with a passage from the Bible enclosed in a case) affixed to the doorpost. The position of the mezuzah is incorrect. It should be higher up on the door jamb and the top should be angled towards the house, not the other way round. (00:15:00)
Factual error: In the infamous Highland bus scene, the driver can be seen issuing tickets from a computerised ticketing machine - astonishing really - the film is set in the early 70s.
Factual error: There is a major error in the scene where Geena Davis steals the tractor trailer. They show a closeup of the brake line between the truck and the trailer being cut. The problem arises when fluid starts pumping out of the line and Geena screams because she's lost the brakes. First, every tractor trailer is equipped with air brakes, so there is no fluid in the lines to leak. Second, if these air lines are severed it causes the brakes on the trailer to lock up and drag the truck to a stop.
Factual error: Casey arrives at the desert landing in a jeep that is flagged with 4 stars (for a 4 star general) although he is only a 3 star general (as evident by the 3 stars on his shoulder boards). (00:33:30 - 00:35:25)
Factual error: When Mel Gibson is leaving NYC by car they come out of the Lincoln Tunnel onto route 4, that is impossible. The only way out of the Lincoln Tunnel is onto route 3. Then when they are driving through New Jersey on route 4, Mel Gibson says "There is the exit for 208." While you can get to 208 from route 4, they were driving on route 4 east, heading back towards NYC, not route 4 west which is the way onto route 208 they showed in the movie.
Factual error: When Xander's thugs are taking the Phantom up to the roof to do away with him, he breaks away and ducks into the machinery room for the elevator. In the scene the door of the room is lockable from the inside only. This door should be lockable from only the outside.
Factual error: The motor cycle race on two Ducatis: they race from downtown Atlanta to Stone Mountain. They are on a road called Freedom Parkway. It exists primarily to get to and from the Carter Center Library - it doesn't go anywhere beyond that really. In the film they race for miles to Stone Mountain, it's about 45 minutes outside the city, and to get there you have to take three different highways. They arrive on one that doesn't exist.
Factual error: In one scene, the pitcher has an Atlanta Braves uniform on and the catcher has a Colorado Rockies uniform on. Unless this was an all star game, how could this be?
Factual error: Although many thing have been changed to reflect the early-mid 80's when the film is set, it is often possible to see 90's cars in several scenes.
Factual error: After the policeman commandeers the old lady's car he finds out quickly that there are basically no brakes. Later he is doing K-turns, and all different maneuvers that aren't possible using a car without working brakes.
Factual error: Throughout the entire Varsity/JV game, the Varsity team makes at least 20 penalties that aren't called. They also refer to a tripping call as hooking, even though the Varsity player obviously goes for the JV players ankles.