Factual error: When McClane and Zeus take the little hatchback from the bank location, they run up the ramp by the Brooklyn Bridge and McClane looks to see the dump trucks aren't on the bridge. Zeus then spots them on FDR Drive and they speed off down the ramp to FDR Drive. The ramp they were on doesn't connect to the ramp they took to give chase. It only heads towards City Hall or over the bridge. They'd have to take the Civic Center ramp, do a u-turn under the Brooklyn Bridge approach then head back up the ramp to FDR Drive.
Continuity mistake: In a major fight scene two soldiers on opposite sides are jumping and spinning and tapping each other on the head with their swords.
Continuity mistake: Hester's estrange husband mistakenly kills a man at the end, and you see him cut his hair and his scalp off, then later when people find his body (after his suicide) his hair and scalp are intact. Then later you see him with the hair and scalp in his hands again.
Continuity mistake: In the first movie, the wedding took place on January 6th. But in the opening sequence here the framed wedding invitation says October.
Continuity mistake: Chili Palmer goes to DeVito's house and parks his mini van next to the curb facing one direction. When Chili gives DeVito the keys for a test ride, the mini van is now parked facing the other direction on the street.
Factual error: If you take the train from Paris to Cannes you won't pass the Eiffel tower.
Continuity mistake: Moving out to Sera, Ben is packing his things in a motel. You can see a half full glass standing on a bed table on his left. In the next shot Ben is pouring alcohol to an EMPTY glass filling it in 1/3 approx. In the next scene glass is half full again and in the next one - FULL. Eventually he is drinking from a glass full of alcohol.
Other mistake: At the end of the first movie Rybak is a Chief (E7), and he is a retired Lieutenant (O3) during this movie. Assuming he got commissioned to Ensign (O1) immediately after the events of Under Siege, it would take a minimum of 42 months to be promoted to Lieutenant. This movie takes place within 4 years of the first movie, because Admiral Bates is still the Chairman of the Joint Chiefs of Staff. The picture of Rybak in his Lieutenant uniform is at least 5 years old according to his niece. None of these timelines make sense for the rank he is in the movie.
Other mistake: Whenever Helen Hyde turns back into Richard Jacks, none of the clothes ever seems to rip or stretch - they both have different body types.
Plot hole: When Charlie sets out to hijack the money train, he jumps off the platform onto the tracks as it arrives, in plain sight of the driver and other passengers at the station, and only puts his mask on once he's in position on the tracks. The train conveniently stops right over top of Charlie, allowing him to enter through the conveniently-placed grate on the train's floor. (01:17:15)
Revealing mistake: When Two Face and Riddler enter Wayne Manor, and knock Alfred down. Alfred, unconscious, pushes the dinner tray aside, so the thugs can carry him into the closet. (01:27:55)
Factual error: Angela Bennett finds the Praetorian's IP while using the PC in the Cathedral's bank: it's 23.75.345.200 - they want us to believe that this is an IP, but no IP can contain numbers greater than 255. [Common practice, like fake phone numbers, but still worth noticing].
Continuity mistake: As Brian lands the plane down to Bangor, his headset is on in a frontal shot, but in a reverse shot it isn't. (00:47:05)
Continuity mistake: Stallone is eating a banana when he is on the computer in the Mariott. He takes a bite and the banana is smaller, then in the next shot it is bigger again.
Factual error: The suits worn by dangerous disease researchers would definitely never tear if the hose was pulled.
Continuity mistake: During the confrontation with Alex's stepfather, Damon Wayans forgot to remove his earring before shooting. Pay attention to his ears - you'll see an earring in one shot and then nothing.
Continuity mistake: At Thanksgiving dinner when the turkey is spilled on her head. In one scene she is wet. The next scene she is dry again and then the next scene she is wet again.
Continuity mistake: When Deebo is riding his bike to Craig's house the first time, one shot shows Deebo nearly on the driveway. Just then Smokey and Craig remove all their valuables. If this were true, Deebo should have seen these. But then in another shot, Deebo's bike is shown just coming onto the driveway. In that amount of time, Deebo should have been further up the driveway.
Other mistake: After the post-bank robbery shootout, a TV reporter is heard describing the shootout as taking place in a "small southland neighborhood." But earlier one of the detectives was heard ordering road blocks at Flower and Figueroa, meaning the gun battle occurred in Downtown Los Angeles. Hardly a small neighborhood.
Other mistake: When Michelle Pfieffer hands out menus for the restaurant in the class, they all read them out loud in English. Then when she takes Raul there, he says he can't read it because it's in French.