Continuity mistake: When Mrs. Fitzwaring shoots herself, she falls face-first onto the pool table, with the front of her left shoulder laying against the table near the narrow side. When Quaid looks back, she's on her back, and now the back of her left shoulder is on the table near the narrow end. Her body has flipped 180 degrees, meaning her feet had to flip over from one long edge to the other long edge. Very difficult for a dead person to do.
Continuity mistake: When the car plunges into the tar pit, the windshield of the car alternates between being covered with tar (starting with Bernard sliding into the tar), to being uncovered (very next scene shows Cookie visible through the window, as well as the gunshot crack) This continues throughout the whole minute of the scene until the car is submerged.