Charles is wounded in the right eye, but when his face appears at the séance, the wound is over his left eye.
Penny removes two shotgun shells from one end of the box on the dresser, leaving two empty slots. Moments later, when the camera pans back to the box, the box is turned around with the empty shell slots on now on the opposite end of the box.
During the seance, the shotgun blast to Charlie's face appeared on the wrong side of his head.
After the seance towards the end, an ambulance is seen to leave the house. This is clearly an American model of ambulance and the siren is an American sounding emergency siren. Neither of these would have been used as or on British ambulances of the early 80s.
The rapist smashes through the French window on entering, yet there is never a mention of having to have the window repaired as part of the cover up, even though it's not something Harry could have done by himself.