The scene in the elevator, towards the end of the film. The button panel is kicked and damaged. Next shot it's intact again.
The scene where Agent Pellman grabs the chainsaw, the power-cord attached to it is clearly visible, still we (The audience) are led to believe that it's a gasoline powered chainsaw when it's obviously an electrical one.
When Alain is fighting with Red Face in the fire in the beginning, as he is striking his face, you can see Red Face's lips are bloodied. However just before his last strike, there is no blood on Red Face's lips.
When Dmitri sends Ivan out of the sauna and the latter dresses himself while pulling out a gun, it's barrel shows a red colored tip to indicate it's a prop gun.