Continuity mistake: When Marvin walks Rianna home after dinner, she stands in front of her door and crosses her arms asking him if he wants to come in. The camera angles from the front show her arms crossed, the ones from the back show her arms at her side. Happens throughout the scene.
Continuity mistake: Near the end of the movie, Marvin meets up with the doctor who tells him that something else is in the woods doing the killing. They both take off running and the doctor falls flat on his back. Marvin turns to go back to the doctor, and the doctor is now sitting straight up and not in the same spot he fell at.