Revealing mistake: The size of the spider walking off Sam's face becomes disproportionately smaller too fast compared to its size while on her cheek plus the spider's awkward movements are indicative of CGI. (00:02:20)
Continuity mistake: A full moon was shown, but it was quite dark even around the campfire. When the man came and said there was something in the field, the sky was black. About a minute later when Cameron tripped/fell, there was (moon) light near the ground. (00:16:09 - 00:18:19)