Numerous scenes that were intended to be filmed at night changes between night and day as the scenes cut from one camera to another.
When battling the Octaman on the river, one of his tentacles is severed. Moments later when the Octaman is seen on shore, all of his tentacles are intact.
Shots from Octaman's point of view suggest a compound eye, yet Octaman's pupil does not have a compound structure. Even if it did, the separate elements of a compound eye act as a pixel in a vision field, not a repeated set of smaller images.
When the group is trapped in the cave, Davido takes their only light source, a flashlight, to climb up the tunnel, yet the rest down below can still see each other clearly.
Early in the movie as the group is driving in the motor home into what appears to be Mexico, they notice a cheetah, which is only indigenous to Africa and parts of the middle east.