Continuity mistake: In the opening scene, following the hitchhiking girls, it is dusk. As the couple drives along, arguing while the man reads a road map, the sky suddenly changes to dramatic cloud action as he comments that it's looking nasty outside, and then a fierce storm instantly brews up.
Other mistake: As the blond punkee pillages the bedroom for anything of value, the unseen giggling/squeaky "doll" voices prepare to attack. She is yanked to the floor by her feet, screaming, as the unseen grab her hands, then proceed to "ram" her face-first into the wall. The large blood spatters do not match the injuries to her face nor her forehead. Also, under normal circumstances, the victim would be rendered unconscious following such force. The punkee is merely a bit disheveled as the unseen toss her outside the doorway.