Other mistake: Pretty much everyone in the film, especially Alice, seems to be able to fire their weapons without reloading at all.
Other mistake: Justin Hammer picks up the M134 like it's a feather. In reality, it's a hundred pound gun, even a big bloke would have to work hard to pick something like that up.
Other mistake: In the scene where Judy and Becca are strapped to beds in the high school and the principal is coming with a pitch fork, at first there is a close up of the fork (when the principal is dragging it) and its dry with no blood, the principal walks over to his first victim and right before he raises the fork it is shown covered in blood so much that some has ran on to the floor.
Other mistake: When Sam Flynn first enters the arcade, he goes to a breaker box on the wall. When he opens it, the breakers are already in the "ON" position, closest to the center. He actually turns them to the "OFF" position.
Other mistake: The lodge the guys are staying in is called The Silver Peaks Lodge. However, in the scene where Nick is confirming his reservation, the sign behind the clerk with the goatee reads The Silver Peak Lodge [singular].
Other mistake: They already stated nobody had TV when the young couple were flirting. Then as the tornado is about to hit the family home Dad rushes to get daughter Sam to go to the basement, and she is playing in front of the TV which appears to be broadcasting the news. Not to mention, if the TV was working, wouldn't most people be watching the news for info?
Other mistake: When Edwin paralyses Isabelle with poison she almost immediately drops down and loses the ability to speak. When he tries to poison Royce and instead gets stabbed in the jaw with his own poisoned blade, Edwin gets paralysed and can't move, but still begs for mercy by saying "please don't kill me" when Royce drags him. (01:28:48)