Continuity mistake: In the 'last stand' covering Mason and Jamie, Vance collapses, hit by the last bad guy he kills; his right hand drops the gun and the assault rifle on the ground is pointing at the red fridge. When he is shown again the position is similar, but different. (01:09:05 - 01:13:05)
Continuity mistake: Vance shot the tank of the forklift the baddies used to break open the riot door, and it exploded in a rather bad CGI animation. The forklift itself looks undamaged after, and when later in the movie Eddie runs past it to momentarily evade Cung Le and go deal with the jammer, the red tank itself is still there. (01:06:55 - 01:13:00)
Plot hole: The bad guys try to enter the mall through the double doors of the entrance, but they do not use the food court entrance, which is undefended. There are plenty of them and there's no reason why they would not use it as main or additional entry point, especially considering that they put a sniper there to guard it (so it's not that they don't know about it), and it's not barricaded, just plain glass doors without even a chain.
Plot hole: Eddie estimates that the bad guys will break through Montclair in 30 minutes. Since they already broke the doors with the first car, and all that remains is a pile of rubble (with a forklift behind, even) that does not stop the passage of a person, it's hard to understand what would hold them back that long.
Plot hole: Once Ben Kingsley has decided that the assault on the mall will happen, the good guys are given an insane amount of time to talk to the kid and calm her, have a nice conversation about what is happening, hole her up in a safe position, observe the vanguard of the baddies scout the parking lot and just then do all sort of A-Team style preparations, barricading the front door and booby-trapping the entrance. The villain is in a rush, knows the layout of the mall and does not fear the unarmed mall cops; there's no way they had time to do all that. Especially since his plan consists exactly of the brute force assault ("driving through" the front doors) that a little earlier Eddie mentioned, contradicting the stated purpose of not drawing attention from passing patrols.
Continuity mistake: Midway through the scene when the guards discuss the intentions of the assailing force disabling their cars, specifically when Vance says "He is now" (in charge), Mason's bag turns around in his arms for no reason. He was clutching it with the colored size closer to his chest, and then it's the opposite. (00:36:05)
Continuity mistake: Eddie and the others are looking at parking cameras; when Vance stands from his crouching position to say "Oh shit, they're gonna find Betty", he brings his hand to his mouth - not so in the following close-up on Banderas, where you see Vance's arm relaxed along his side. (00:35:35)
Continuity mistake: Jamie is holding at (toy) gunpoint Eddie; she has her thumb on the 'barrel', but it cuts mid-sentence to a close-up as she says "You don't cut me out and don't talk to me like a child", and her thumb is now on the 'fore-end' (if it makes sense with a toy weapon). (00:31:25)
Continuity mistake: Eddie is taken into the staff room to be introduced to the team and on the wall there's a big digital clock, making rather obvious the various takes combined in editing, creating a bunch of errors in continuity. When Vance starts mocking Mason, the clock is on 8:48, going back to 8:47 when Mason stands up from the chair. Ruby enters the room and the clock flips from 8:47 to 8:48 at the very first cut. (00:15:00 - 00:16:00)
Other mistake: Introducing the workplace to the new employee (Banderas), Vance says that the mall has never been updated because it has everything "Menswear, kidswear, ladieswear, cosmetics." The Italian dub misinterprets the last word (probably figuring it was 'medics'), and so the mall has the rather unlikely lineup; "Menswear, kidswear, ladieswear, doctors." (00:14:20)