In the beginning of the movie, when Billie detours to go to the lake, the front driver's side wheel cover is missing, and looks like some minor front end damage in the same area, which can be seen when she pulls up and stops next to the bush at the lake. Later on in the film, the wheel cover is present and there is no damage to the car.
The goof item below may give away important plot points.
After Rosie and Varla take out The Old Man with the Porsche, the front license plate is shown hanging down. Later, when the Porsche is shown approaching The Vegetable, the license plate is back in place.