Deliberate mistake: It would be impossible for anyone to push up on a casket lid six feet underground and make the lid move much less crack enough to get their whole body through, the dirt would fill the box and trap the occupant.
Other mistake: Driving down the highway, Zane spots an old, ugly woman. He swerved toward the right side of the highway. When they are done talking, he is seen leaving from the left side of the highway at the dirt.