In "Joy Ride" they make a point of the car having a broken tail light when the killer begins to stalk them. After they get the car repaired they get the tail light fixed (making a BIG point to say it's been fixed and showing that it's now working). Yet later in the movie after Charlotte is held hostage, the car pulls off the road by the corn field following Rusty Nail's directions. Look at the car's tail light. It's broken again!