Other mistake: In the scene where Ecks is chasing Sever, you see Ecks put a shell into an open chambered shotgun. This means that there is only one shell in the gun. A moment later when he yells stop inside the building he cocks the gun again. Thus, he is holding up Sever without any shells in the gun.
Factual error: In the scene where Lucy Lui blows up Vancouver city police cars they are depicted as dark blue. Vancouver police are white and green.
Plot hole: Since when do highly trained, professional police/SWAT operatives run lemming-like at perpetrators in an armoured assault vehicle with an M-60 in it? This wouldn't happen.
Continuity mistake: How does Ecks survive being buried under seemingly TONS of metal pipes without breaking any bones in the process? Also, the first shot of the falling pipes scene buries him completely, but when the henchman is looking for him, Ecks's body is exposed from the waist up.
Revealing mistake: In the closeup of the M-60 mounted in the assault truck in the big shoot-out, the linked ammunition has no primers in any of the bullets.
Other mistake: Near the end in the train yard when everything was blown up there was a passenger train car still in tact with its windows still in it. The train car next to it was levelled.
Continuity mistake: In the long shot of the sniper falling down onto the car, you can see that there is nobody standing next to it. Yet when the crash sends the tyre flying, suddenly some policeman is right beside the car getting hit.
Factual error: Why are the FBI investigating and following their case if it's in Canada? The FBI or any other law enforcement agency in the US has no jurisdiction in Canada.
Factual error: After Ecks has just been buried by the metal pipes he shoots the guy who comes to kill him. He then uses his gun to help him up. I know someone who was in the army. Rule number 1. Never put your muzzle in the dirt. Then Ecks put his weight on the gun, forcing it deeper into the dirt. (01:11:00)