During the home invasion scene, the boy can be seen breathing after being killed.
In the opening shot of the movie of a woman's body, the "dead" woman (Mary Demas) takes a few breaths towards the end of the shot, as seen by the movement of her stomach. The filmmakers point this out in the commentary, and show additional footage in the outtakes.
Some obvious matte lines are seen in the film from time to time.
When the lady in the blue sweater leaves the mall, she gets into her Black car, puts the car into reverse, backs up, then continues forward without putting the car into Drive.
(around 46 min.) When the high school kid gets into Otis' car to share a blunt, the operational camera crew is vaguely reflected on the car door as it swings open.
Just after Becky buys a newspaper and sits down to read, a vehicle goes past and we see a camera on a tripod to the far right of the shot.