Other mistake: When Harry gets to his vacation spot he is greeted by a dog. A few seconds later the dog is seen lifting his leg to pee, showing his dog is a male. Later on in the film after he returns home after the main killer has killed the second victim, the dog is scratching at the door. If you pause the movie at this moment you notice the dog has a sagging belly with nipples just like a female dog after delivering puppies. (00:48:05 - 00:57:20)
Other mistake: Jennifer's surname is spelled as "Spencer" in the closing credits, but on a sign in the gallery it is spelled "Spenser."