Continuity mistake: When Clay and Jenna leave the lodge and walk over to his motorbike Clay has his bag on his left shoulder. In the next shot it is instantly in his right hand. Then when he sits on the bike the bag is still in his hand, but in the very next shot it's suddenly back on his shoulder.
Continuity mistake: Near the end when Jason is fighting with Clay in the barn, Clay's face is relatively dirty and sweaty. But in the shots when Jason is trying to force Clay's face into the rotating blades, his face is very clean and dry. Then in following shots it is dirty and bloodied up again. The cleanliness of his face does differ through the whole scene.
Continuity mistake: When Clay and Jenna are at the camp and are about to leave, but Clay's flashlight runs out of batteries, he digs into his bag to get more, but they spot Jason so he leaves the bag and hides. Jason finds the bag and takes it with him. When they're leaving the camp, Clay's flashlight is working again.