Revealing mistake: As the Camaro explodes on the bridge, a piece of it notably flies off. You can see it fall down a cable attached to it. (01:12:20)
Audio problem: We hear Mike cock his two guns a variety of times in a row during the scene when he is threatening Jojo and Marcus. (01:25:25)
Continuity mistake: After the truck smashes through the drug deal location, there's a brief intermission with Julie trying to open her cuffs, saying "Go, go, go," and then Sanchez fires at a bad guy on the scaffolds, killing him. A few seconds of hectic action pass, Julie detonates the barrels, and Marcus looks up and shoots another villain on the scaffolds. As he falls, you can see another one close by; it's the same guy who died earlier. (01:44:50 - 01:45:25)
Continuity mistake: Marcus opens a locker inside Mike's house and fetches two boxes of ammo from it. Look at his body when he is about to close it; he reveals the content of the locker, with a pair of handcuffs shining in the darkness of the bottom shelf. When Julie looks inside to get her handcuff keys, the handcuffs themselves are in a different part of the locker. (01:30:00)
Continuity mistake: When Marcus's sons yell to call their mom, in the first shot she is holding sunflowers, keeping them straight, stem fully vertical. In the next shot, it's at an angle. (01:29:40)
Plot hole: Marg Helgenberger's investigation reveals that the mole has called Club Hell from the precinct. However, if you look at the scene, the villains are not expecting them (Casper spots them practically by accident and asks out loud what the cop is doing there; Noah looks incredulous), and they are even having their ether traffic in the open at the club front. Note that technically it does not say that a call was made before the blitz, but considering the mole knew about it first-hand, it's unfathomable they wouldn't tip them off. (01:23:15)
