Revealing mistake: Near the end of the film where Proctor kicks the chair towards Harris, if you look closely you can see the two grooves/rails that the chair slides along.
Continuity mistake: When the bad guys are stealing jewelery from the Museum Of Fine Art, they cut out part of the glass with a laser. The shot changes during cutting and the position of the jewelery inside the pyramid is different than in the previous shot.
Continuity mistake: When the 6 bad guys and Lassard are in the elevator and one passes gas and the rest move over, the bald guy (with blue tie) is against the wall. When the shot changes to an overhead view, he's now in front of someone who's against the wall. When the shot changes back, he's against the wall again, next to the guy he was just in front of.Bishop73