Continuity mistake: When Bert returns from shooting, he talks to Jeff and Marcy, when returning his BB gun hangs over his right shoulder. Shot changes and his gun hangs over his left shoulder. When it cuts to the last back closeup of him and as he walks away to the cabin, you can see the gun has jumped to being over his right shoulder between the shots.
Continuity mistake: After Paul uses the Listerine as a disinfectant, there's a closeup on the bottle and you can see that the level of the Listerine left inside is just below the word "Listerine" on the label. Every time the bottle is seen after that, the level of liquid is higher.