Continuity: Tracy's hair in elevator in beginning of movie
Continuity: Tracy (not) embracing Jed in their last scene together
Revealing mistakes: When Andy visits the house by the cliff, the back door is swinging wildly in the wind. However, the pouring rain comes down perfectly sraight.
Continuity: The doctor's address on the Rolodex card is 36 Hedges Lane, but the mailbox on the house states 38 Hedges Lane.
Continuity: When Andy and Tracy go smashing through the banister, the CPR dummy which Tracy is holding is dropped on the ground. However, moments later, the dummy is shown propped up against the banister.
Errors made by characters (possibly deliberate errors by the filmmakers): Jed said Tracey's blood group was AB negative. He would need to get donors in that type. In fact she could have been given any Rh negative blood type. Group O, A or B would be suitable for someone who is group AB (universal recipient). Only the Rh type (positive or negative) is important and then only to woman of child-bearing age.