When Matthew rapes Jennifer, his glasses have no lenses during a close up shot. This may be due to the director not wanting any sort of reflection showing up in the lenses during that shot. The lenses reappear afterwards.
The goof items below may give away important plot points.
It would be physically impossible for Jennifer to lynch Mathew as depicted. In a pulley situation, one cannot hoist greater than one's body weight, regardless of strength, unless one is somehow anchored to the ground.