When Emily leaves her house and gets into the Cadillac, the license plate reads 'ATH 3' but when she and Vincent are in the parking garage it reads 'ATH 2'.
After Emily and Vincent walk back to the hotel, Emily has Vincent's jacket on. When they walk into the room, she still has it on but when they walk outside again, Vincent is wearing it.
When Vincent and Emily drive to a bar, only one person is visible in the car as they round the bend.
The emblem on the BMW trunk disappears.
Near the end, when Emily drives the Cadillac into the parking garage, she parks leaving the front wheels turned. Moments later, as she and Vincent are sitting in the trunk, the wheels of the car are pointed straight.
At the end of the movie, when Vincent closes the trunk of the Cadillac Deville with his leg, there is a distinctive latching sound of the trunk. Cadillacs do not make such a sound since they have a motorized trunk-closing mechanism which closes the trunk silently when the deck lid is closed gently. It is impossible for a Cadillac to make such a sound as the one in the movie (unless it was modified).
Reflected in the side of a big, silver semi which passes in front of the camera as they approach an interstate.