Continuity mistake: Right after Bennett takes off in the plane, Claire throws a gun to Alice. Between the slow-motion shots, the gun switches position in mid-air before Alice catches it. In the shot of Claire throwing it, the barrel is facing to the right, meaning that it should be facing to the left in the shot of Alice catching it. But it still faces the right when she does.
Other mistake: Wesker's chamber on the Arcadia has only one entrance, a big blast door which Alice walks through. Yet Chris and Claire manage to appear behind Wesker without the blast door ever being opened.
Continuity mistake: During the first fight, the boots of Alice change from high heels to no heels and back to high heels several times.
Other mistake: Pretty much everyone in the film, especially Alice, seems to be able to fire their weapons without reloading at all.
Audio problem: Near the beginning of the film when Alice and her clones break into the Umbrella building, she comes down in an elevator. The numbers above the elevator showing what floor she is on beep every time they change, but some of the beeps are out of sync. A beep is heard for floor 6 before the number 7 has even changed and a beep is also heard a fraction of a second before the number 3 fully appears.
Continuity mistake: During the scene on the rooftop, after shooting some approaching zombies, the group run into the lift while shooting a bunch more zombies. The bomb then explodes, sending the lift down. The scene goes back to Alice fastening herself on a sling. When the camera moves to show the zombies, all of the zombies have moved back some 25 feet away and all of them are standing still, waiting patiently for Alice to make the next move. Alice turns around to run to the edge of the building, and we can see that the zombies who had been shot earlier and should still be lying around have magically disappeared.
Continuity mistake: When K-Mart throws Alice's shotgun to her right before she shoots Wesker in the mouth, between the slow-motion shots, the gun switches position in mid-air before Alice catches it. K-Mart throws it with the barrel facing towards Alice but when she catches it its barrel is facing away from her.
Other mistake: At the end of the fight with the Axeman, Alice points a shotgun towards him, while both she and Claire are sitting on their knees (as is seen in the overhead shot with the axe in the wall). But the shotgun is clearly pointed downwards. Alice is 5'9'', while the Axeman is at least 9 ft. tall. If she wants to blow his head off, she should have been pointing it more up.
Continuity mistake: During the scene where Bennett takes off in the plane, the concrete edge suddenly disappears. He hadn't already taken off, because he makes a huge dive directly after leaving the roof, and even if he did use it as a ramp, then it makes no sense why Alice did smash through the edge.
Continuity mistake: When Alice makes the first approach to land on the roof of the prison, Luther shouts "Down!", and they all duck. In the close up shot of the group, you can see that Angel and Bennett are facing the same way as Luther and Kim. But in the wide shot, they are facing in the opposite direction.
Factual error: Alice isn't superhuman in the scene of the Tower Swing. But at the rate she is falling, she would both hit the ground before the cable would be under tension, and even if the prison was high enough, it would probably shatter every bone in her shoulder when it does become tensioned.
Continuity mistake: During the initial fight scene, the clone who survives the Needle Dive is later on shot by Wesker, upon which she drops two grenades. Where did she pull those grenades from? Right before she jumps out of the window, you can see that there are no grenades dangling from a belt, and there isn't much room to hide something like that in a skintight catsuit.
Deliberate mistake: When Alice jumps from the rooftop, the entire roof explodes, but the wire she is on is still intact.
Revealing mistake: Just before the group enters the elevator which Alice blows up, they are all shooting at the horde of zombies. But pay close attention to Alice's MP5K. There are no empty shells flying away from it, which means the gun ran out of blanks and the flares were edited in later on. Also, we can see the empty cases flying away from Luthers gun, who is even further away from the camera.
Continuity mistake: Alice drops her shotguns after she is knocked out by the Axeman, and a close up of the shotgun shows that it lands near one of the shower columns. And when Claire spots the shotgun, it is still lying in the spot where Alice dropped it. But in the wide shot just before Claire starts her slide, the one with both Claire and the Axeman, there aren't any more of the shower columns between them, and Claire only picks up the shotgun after the wide shot.