When the anaconda chases Amanda in her car through the forest, she looks in her rearview mirror, and the snake is slithering on a road. In the next shot, there is clearly no road, just the forest floor.
When Jackson, Scott and Roland arrive at team one's dig site to find the corpses of team one in the excavation, the corpse on the left can be seen visibly breathing.
When Amanda falls from the ladder, the bottom rung breaks in two. Alex then climbs down the ladder, and later back up the ladder using the bottom rung.
Amanda falls from the ladder and is seen prone on the ground inches from the bottom of the ladder. After Alex climbs down, he steps over to her and she is lying further away from the base of the ladder.
During the car-snake chase, the 4WD is driving along a bitumen road. It then hits a dirt mound on what is clearly a gravel road.
Just before the title sequence, when the camera enters the lab, the cameraman can be seen reflected on the edge of the stainless steel worktable. He's wearing jeans.