Continuity mistake: In the scene where Elena gets killed, when she starts to run her shorts are around one ankle but 2 seconds later her shorts are all the way up and buttoned.
Visible crew/equipment: When Kimberly is cut in half, you can see the crew reflected in the car.
Plot hole: When Amber and Jonesy are running from the cannibal with the arrows, they are running slow and acting like they aren't even being chased. And Amber gets her shirt caught on a tree and has to slow down to put it on?
Revealing mistake: After M gets his head cut off, you can see him breathing.
Revealing mistake: When Dale takes the necklace off Mara, you can see her breathing when she's supposed to be dead.
Answer: It's just a prop to make the game more realistic.