Factual error: In the amount of time it took for Arnold to exit the lake and infiltrate Khaled's party, the mere temperature in the mountainous region would freeze the hole over long before the patrolling guard would come across it. It might not be fully frozen, but enough to be mistaken for being normal to the casual observer.
Factual error: When Arnold's harrier hovers up and a terrorist has to adjust the focus of binoculars, it shows Arnold's face. Being so close, there would be no way binoculars would have a clear view of his face, maybe a blurry eye at best.
Revealing mistake: When the motorcycle is jumping off the hotel roof, the background scenic is visible. The scenic is a large backdrop with an image of the night skyline. If you look in the background above the white tower, the hazy sky stops before it reaches the edge of the movie frame. This is also visible in the shot where the horse runs toward the edge. (00:39:43)
Continuity mistake: When the wall is taken off Simon's trailer, he falls on Helen and he knocks the champagne bottle off the table in the process. When Harry knocks the table aside, the champagne bottle is back on it.
Visible crew/equipment: The first time we see Salim Abu Aziz on the Florida island, he has his back to the camera and turns around. The shot comes closer to him. The camera shadow becomes visible on him at that time.
Continuity mistake: When Helen is inside the caravan the way she holds the glass changes between shots.
Revealing mistake: When Arnold uses a hose as a flamethrower, the terrorist on the left has his head and face soaked in fire retardant gel. (01:44:47)
Visible crew/equipment: When Harry seats in the Harrier a pilot wearing sunglasses stares at him and stage lights are reflected on his lenses.
Continuity mistake: During the fight in the limo between Jamie and Juno, some stray shots go through the roof, creating obvious bullet holes. They change quantity and position a few times in the subsequent shots. Also, in the shot when Arnold lifts Jamie out of the limo and it takes a header into the water, the bullet holes are completely gone.
Revealing mistake: When Aziz (Art Malik) goes flying stuck to the missile, you can see a blue harness under his shirt just before he hits the helicopter. Only noticeable in the close up shot of his face and body.
Revealing mistake: When Aziz (Art Malik) shoots at Harry (Arnold) in the bathroom, he has a rifle with two magazines taped together. If you look closely, the second magazine taped next to the one in the gun is empty. He then reloads the gun by flipping the second, empty, magazine and loading it.
Visible crew/equipment: After Harry finds out Helen is cheating on him with Simon, there is a scene at the house where the camera pulls in on the family eating dinner. In this shot the shadow of the camera can be seen creeping onto the windowsill.
Audio problem: When Harry is walking across the street after finding out Helen is having an affair, the bus beeps its horn but the driver's hands remain on the wheel.
Continuity mistake: When Jamie first enters the hotel room, she moves up to the table with the champagne on it. But, moments later, she proceeds to move up to the table again, right before Arnold says hello.
Other mistake: During the bathroom shootout scene, the terrorist shoots the bathroom stall walls from a heavy angle. When the walls and doors are shown from the front while being opened, the bullet holes go directly through both walls of the doors, which would only look like that if they were shot from directly in front.
Continuity mistake: When Jamie Lee Curtis and Tia Carrere are fighting in the limo, their hands can be seen wrestling for the gun on the roof in one quick shot before that action actually happens.
Continuity mistake: When Tom Arnold introduces Arnold Schwarzenegger to the remote camera eyeglasses, Arnold sees his daughter stealing money from his jacket. In two camera cuts, the angle and width of the remote camera view changes, although the remote camera is stationary on the fireplace mantle.
Revealing mistake: While the credits roll, Harry enters the Swiss mansion, the camera turns to a green-coloured night-vision filter and one can notice that the man entering the house is Harry's stunt double.
Revealing mistake: When Arnold horseback rides towards the hotel, Tom Arnold's van skids and you can see that he is a stuntman with a very cheap latex mask to resemble Tom.
Plot hole: Harry goes into the Mall, and two of the terrorists follow him through the Mall, up the escalator, down the hall, and into the men's room. Then the third terrorist leaves the car and follows exactly the same path to where the other 3 went, even though there's no way he could have known exactly where to go.
Chosen answer: He didn't really. Harry just knew he was heading up. He pressed the top floor to get the elevator moving and kept an eye on him on the way up. If the terrorist's elevator suddenly stops, Harry can press the button for that floor to stop his elevator.
XIII