Towards the beginning of the film, when Alex sings "Always Keep An Edge On Your Knife" in the car, the car switches lanes between shots.
At the advanced stage of decomposition of the deer, the eyeballs would have been long gone. Instead, they are prominent and intact. Clearly fake plastic.
Alex gathers firewood, and comes back with an armful of rotten wood, which is useless because it won't burn on a campfire.
Fish guts would have drawn the bear and other animals to the campsite.
It has been noted that a lake could not be found on the summit of a mountain or hill and thus it is a major writing or character error for the couple to be climbing in search of the lake. But in fact, volcanic and glacial activity can form lakes high up on or at the peak of mountains.
Near the beginning, the main characters take a selfie shot with a BlackBerry Bold. This isn't possible because the BlackBerry Bold does not have a selfie camera.
At 0:37:22 -a member of the crew has brushed against a tree limb, causing it to sway back and forth.
The morning after meeting the Irishman Jenn gets up to find coffee, and breakfast are already made. Alex pours her a cup of coffee from the pot that is fresh off the fire, into a metal blue enamel cup. She holds it with her hand wrapped around the cup. Either she has no nerves in her hands, or that was not actually fresh, hot coffee.
Jenn's microphone is clipped too close to her neck which muffles her voice.
From 0:07:14 -the actors haven't been taught how to properly paddle a canoe.
Hollywood cliché #058: -it's impossible to move through the woods without injuring oneself.
Alex drops the canoe on his foot. It is later revealed that the canoe somehow splintered and managed to drive a piece of wood under his toenail.
Walking, unassisted, on a leg with a compound fracture.
Campsite or not, pissing near the food is unacceptable. He should have been asked to move away.