Continuity mistake: After they find Rebecca's body, Rios asks Sarah if she can remember anything. She replies with "We shouldn't stay here." Between these shots, the thickness of the dirt on the right side of Sarah's mouth/cheek changes. (00:27:15)
Visible crew/equipment: A crew member's bald head can be seen peaking in the bottom right hand corner of the shot as the sheriff moves his torch around. (00:32:00)
Revealing mistake: While Cath is trapped on the other side of the fallen boulders, Dan tries to move some of the rocks to get her out. You can see one of the rocks by his feet move as if it is made out of foam. (00:34:25)
Continuity mistake: After Sarah and Rios come out from the flooded cave, their clothes are bone dry even though there were almost fully submerged underwater. (01:01:25)
Factual error: Rios records a message for her daughter on her mobile phone. The phone is a Nokia N81. The film is set two days after the first one, in 2005. But the N81 wasn't released until 2007. (01:02:00)
Continuity mistake: When Vaines takes out his gun whilst using the camcorder's night vision mode, the condition of his thumbnail in the close-up shot of him taking out his gun looks completely different to how it is in the close-up shots of him holding the camcorder. In the gun shot it looks dirty and unkempt but looks clean and pristine in the camcorder shots.
Revealing mistake: When Sarah, Rios and Juno are fighting the Crawlers at the end of the movie, Rios beats one of them to death with a rock and kicks its head open. The head is clearly made out of rubber or some sort of prosthetic.
Plot hole: If the missing people were already in that cave, then why did they have to cut locks of the building and pry boards off the hole?
Continuity mistake: In the scene where Sarah and Ellen are attacked in the pool of poo, Ellen stabs one of the creatures in the neck with a hair pin. Sarah ends up with blood all over her face, her neck and her (white) jacket, moments later there is hardly any blood on her, which later reappears.
