Other mistake: Although the Lieutenant is actually sent to the police station in precinct 9, division 13, the sign over the door states it to be division 14.
Other mistake: Ethan Bishop says to Wilson in the hallway as they plan their last stand "acetylene tank, magnesium flares...I stand in the doorway with my rifle, I shoot the flares, they ignite the tank, we blow the hell out of everybody in this hallway" But why can't he just shoot the tank directly as that would ignite it? Then it would be easier as a bigger target? Just igniting flares alone would probably not ignite the tank anyway as they would not have enough force to pierce thick metal. As he said in previous scene about the tank "if a stray bullet had hit this..."