When the monster truck rams the back of Adam's car the shot immediately after shows no damage at all to the back of the car. This happens in several scenes throughout the film until the car is eventually destroyed.
Adam traps Harley's head in the car window which is shown to be a power window. Other views of the car's interior shows a manual window cranks.
A short while after Harley shows up driving that Monster Truck, two unexplained blood spots appear on Adams shoulder.
When Sarah cuts Adam's t-shirt, he is wearing a black t-shirt under the green one. But when Sarah and Adam made love, there was no black t-shirt under the green one.
When their car breaks down, Harley says "these vista cruisers usually run forever". Later on, in a shot of the front of the car the grille has a Chevrolet emblem, the Vista Cruiser is an Oldsmobile.
When Adam just gets to "Monster Man's" house, he is hiding behind one of the monster truck wheels. The rim has a black recess in it, where it would be hollow, however you can see his reflection. These rims are obviously cardboard.