Minor Plot hole: Royce realizes that there is something weird about the planet: the sun doesn't move. And yet, most of the movie takes place at night.
Minor Plot hole: When the predator dogs attack the 'heroes', it takes 4 gunmen and entire clips of ammo to take one down (they don't miss their shots). Surprisingly, the last dog requires only 1 bullet while another one could be killed with a machete.
Major Plot hole: Near the beginning of the movie, Isabelle mentions that one guy survived against a predator using mud to become invisible to the alien helmet vision. However, no one wants to try it out until it works successfully for the main protagonist when almost all of the other humans are dead. (Speaking of which, how can mud completely cut heat emissions ? )
Major Plot hole: When the larger Predators tied-up the smaller predator to a cross, they decided to leave all his equipment and weapons just beside him so that if he could be freed, he could smoothly put all his equipment back on and hunt the predators with a full and efficient vengeance.
Unaddressed Issue: The predators have the technology to make their spaceships explode from afar. Would it be that hard to add the option to LAND the vehicle instead of blowing it up ?
Unaddressed Issue: Edwin, the doctor of the group, is able to recognize and know the name of a plant and toxin that is found on an alien planet.....how ? Did the aliens bring human plants to the game planet ? Why would they do that ?