Revealing mistake: Near the beginning of the film, an axe is thrown at a priest. The axe should rotate as it travels, because the head is heavier than the handle. But it hangs upright as if drawn by a wire.
Continuity mistake: In the scene where Maggie goes to the restaurant with Bob, he offers her the case where the weapon is. Bob says, 'It's loaded'. Close inspection shows the clip chamber is empty (not loaded), and a cartridge clip is positioned beside the weapon in its tailored slot in the custom case. Maggie closes the case and says, 'I don't understand.' After Bob explains what she is to do, then leaves, Maggie opens the case again and suddenly there's a clip in the weapon (loaded) and another one beside it. The weapon was not loaded when she looked the first time.
Plot hole: A nuclear armed stealth fighter is accidentally sent back in time to 1940's Nazi Germany. After the Nazis capture it, two days later they drop a nuclear bomb on the United States. There are several basic problems here. Firstly, if the Nazis captured advanced technology, wouldn't they spend more time taking the plane apart and interrogating the captured pilot? How on earth did they manage to train a pilot to fly the stealth in such a short length of time? And how did the stealth fighter manage to reach the U.S. from Germany when in-flight refuelling was unknown then?
Continuity mistake: When Joe, the Heisman candidate quarterback, jumps his Harley off of a dirt cliff, one camera angle is from below as the bike is in the air. The angle clearly shows the bike is different from the Harley he started and finished with. Most noticeable is the fact that the tyres on the stunt bike are knobby enduro tyres, but later when the bike is stopped, you can see the smooth street tyres are back again.
Factual error: During the scene where Bruce leaves his girlfriend's parents home, it's raining. He leaves in a huff on his motorcycle and you can clearly hear the sound of screeching rubber on the pavement. Peeling out and making this sound would not have been possible in a rainstorm.
Continuity mistake: During the final fight between Jean-Claude and the bad guy, they are both holding onto a shotgun. Initially the barrel of the gun is in J-C's left hand. But without either of them letting go of the gun, suddenly the gun switches end-for-end and the stock of the gun is in J-C's left hand. It looks like they probably re-filmed the last of the fight so the bad guy could use his right hand to hit J-C with the butt-end of the gun.