Revealing mistake: In the disco scene, the DJ is playing music, but the Pioneer decks and the DJ Mixer are not even turned on, as no lights are showing.
Revealing mistake: When Eric Matthews is smashing his foot, he hits it the first time and it shows a close up. If you watch the small amount of blood when he hits it again they have used the same shot. (00:04:00)
Revealing mistake: During the final conversation between Detective Frazier and Arthur Case, Frazier holds up his hand with the ring on his middle finger. It is pretty obvious that the hand was inserted into the scene in post production; the hand doesn't move in a natural way and simply looks out of place.
Revealing mistake: When Costello's men drive off, after throwing Queenan off the top of the building, the state troopers are firing at the van. One back window is shot out, then in the next shot of the van the other window is shot out and then the same one is shot again so the one window is shot out twice in the same scene.
Revealing mistake: In chapter 14, Bill Cox calls Harry, who's asleep in bed. Harry answers his flip phone, but doesn't flip it open. (00:54:50)
Revealing mistake: When Jack drives the bus down the alley, it knocks a series of A/C units off a building. The last one comes open and there is obviously nothing inside. (01:12:35)
Revealing mistake: After John and Nelson are led to their prison cell, Nelson walks to the toilet and starts complaining about how disgusting it is. When Nelson steps away from the toilet, he breaks down in tears and let's himself fall backwards against the 'stone' prison wall. The wall is seen moving, which reveals it's not a real stone wall, but made from a softer material, like wood or plastic. (00:25:15)
Revealing mistake: When Lee is being lifted into the incinerator, he moves his head, despite being dead.
Revealing mistake: When everyone first gets off the bus outside the hotel, Williams shakes hands with Margaret. If you look at his wrist you can see his real skin, not the prosthetic which is supposed to go nearly up to his elbow. It can be seen a little better in the next shot as well.
Revealing mistake: Right after Sage plays chicken with the cops, the cop car is shown peeling out in reverse to follow her down the alley. The dust from the burnout is ejected towards the back of the car. Being a Crown Vic, the car has rear wheel drive but the dust should be moving opposite the car's direction. What this shows is that the car was actually being pulled backwards as it attempted to accelerate forwards. What's more is that even the sound is of a car spinning its tires opposite to being dragged. (00:12:50)