Before rappelling of the cliff, Joel switches his yellow and blue Asics for some more appropriate footwear. In the next showing him rappelling of the side of the mountain, he is seen wearing the Asics. In the next scene, he is wearing the hiking boots again.
During the first facial closeup of Gail's dead body upon discovery by the park ranger, Gail's carotid artery clearly has a pulse.
The deformed side of Karel Struycken's face switches from right to left to right again.
In the close-up of the dying lantern in Greg's hands (about 38:30), the brim of a hat can be seen in the corner of the frame, but in the long shot Greg is not wearing a hat.
Characters' voices don't match lip movement; numerous instances within the first 5-10 minutes.
The killer's deformed appearance was the result of burns that he received in a fire and is not his original appearance. So, the baby that he had with Nancy would have a normal appearance and she would have no reason to scream.