Revealing mistake: The final scene is filmed in Brant Rock MA, and the weather is blatantly CGI. If you notice almost everyone is bone dry in a supposed driving rain storm. Look especially at the character perched on top of the submarine tower. For contrast note the "pizza delivery" scene where it is raining heavily and everyone involved is soaking wet.
Revealing mistake: During the police chase with Gabriel on his motorcycle, he stops and turns to start shooting at one of the cops. By appearances, Gabriel is using a standard Glock which had a magazine capacity of 15 rounds. He has no extensions on it at all with the handle and magazine visible. Yet he proceeds to fire the gun 33-35 times at the cop car without reloading and in continuous fire. (00:57:55)
Revealing mistake: During the big shootout on the freeway at the end of the movie, there is a camera pan over all the cars stopped in traffic. There are no people in any of the cars. The shot is so high that you would still be able to see people crouched down if that was the case. (01:56:47)
Revealing mistake: As Will and Ben are wrestling for the gun, it goes off, shooting Ben in the chest. When you hear the shot you can see the gun is lying on Ben's chest with him holding it, and it's pointed pretty much at an exact 90° to his side. It would have barely grazed him at best and would have left a long scratch/cut at that angle. Yet as they get up the shot is perfectly centered on his chest and round as if it was a direct shot. (00:24:55)
Revealing mistake: After Frank shoots Kevin and Kevin's SUV hits the curb, the background/scenery changes as well as the position of Frank's car. Frank initially pulls along the curb (behind the SUV) with his car at about a 30° angle. The next time Frank's car is shown, it is almost perpendicular to the curb and the Food Mart. When Rupple and Frank have their guns aimed, they would be aiming inside the Mart, not toward Kevin. Objects in the background also change (e.g, fire hydrant, telephone pole appear). (00:16:48)
Revealing mistake: When Gotti shoots the man taking a shower, he is running his fingers through his hair, but it is apparent that his hair and body are practically dry. It is also clear that the man is not actually standing under the running water, but in front of it. (00:11:00)
Revealing mistake: When the agent is questioning Fat Freddy after the cop finds him with coke and a gun, she puts a phone up to his face and says "say cheese." She holds the phone up to his face with the screen facing him. You hear the click and beep of the phone taking a picture, but when she turns the phone around, it's still on the locked screen with just the background and a clock. (01:06:45)
Revealing mistake: When Velma sabotages the science project making it explode into purple goo, you can see that the vial of chemicals she tampered with simply spray around clean liquid, and the purple goo falls from above. (00:23:55)
Revealing mistake: At the beginning of the movie, the protagonists dump the corpse of an agent in the middle of nowhere. The guy is stone cold dead...but you can see the carotid pulse on the right side of his neck, under the fake blood. (00:03:10)
Revealing mistake: When Bu is packing up his things in his bedroom, the camera appears to sway abruptly from side to side two or three times during the scene, almost as if the cameraman couldn't keep the camera steady. (00:57:25 - 00:57:50)
Revealing mistake: When the bartender recognizes Harold and calls the cartel leader, his phone screen stays on instead of turning black and shows that he's still on the lock screen displaying the time, not actually calling anybody. (00:49:30)
Revealing mistake: Stephanie is browsing on the library computer the copy of The Cherry Creek Observer. On the page at the right end of the screen you can see under a title about an assault, a copy-pasted article about autism. (01:20:20)
Revealing mistake: Gone past Waikiki who tells him he knows about the cop, Everest wheels her to the secret door. Batista to open it touches the leftmost corner of the slat. In previous close-ups, the button was at much greater distance from the wall, surely not just an inch. He's pushing no button, just pretends to. (00:56:30)
Revealing mistake: During the car chase, there are a few brief moments where you can get a look at the stunt-drivers who are driving the cars in the wideshots. They look similar to the actors... but not exactly the same.