At the ranger's office when the security guard was stealing the medical supplies, you see a cameo of M. Night Shamalayan in the reflection of the glass.
Continuity mistake: When Ivy was talking to Lucius about how her older sister is spoken for, and how she is free to receive interest, her hand is on the other side of the pillar from her. When the angle changes, her hand is wrapped around to the front and she is almost hugging the pillar.
Continuity mistake: When the two villagers throw the slab of meat on the rock for the creatures, it lands rib side up. A second later the meat is shown from a different angle, and now it is lying skin side up.
Continuity mistake: In the scene where Lucius first goes into the woods, he picks a branch of berries off of a bush. The size of the branch and the number of berries on it is different when he is walking out of the woods. There are more berries and the branch is bigger than when he picked it.