Revealing mistake: Right at the beginning of the boat chase when Bond drives the boat through the waterway in MI6, before he jumps the boat into the river, there is a shot roughly from Q's POV, the boat clearly slows right down before it reaches the end. It couldn't fly as far through the air as shown.
Revealing mistake: Near the end of the movie where Renard and Bond are going at it, Bond is choking Renard and vice versa. You can clearly see Bond's thumbs aren't even touching Renard's neck.
Revealing mistake: During the action sequence on the labyrinthine docks on the Caspian Sea, one of the choppers with the rotating blades saws Bond's BMW in half. A cutaway shot reveals Bond nearby, murmuring, "Q's not gonna like this." The next shot is in back of Bond, seeing the newly split BMW fall apart, but Pierce Brosnan has been replaced with a dummy. This is most obvious during the over-the shoulder shot of the BMW falling apart, where Bond's gun is now held in front of him. Also, when the car splits in two, the dummy shakes a bit.
Suggested correction: The over-shoulder shot is not clear enough to reveal a dummy; when the car splits in two, the whole boardwalk around it shakes, as would the real actor/double.
