During the scenes where Ace is under attack by the poachers in the woods, part of his shirt falls off of his shoulder. In the next couple of shots, the side of his shirt that is off is back on his shoulder.
When Ace is in the Production Room and makes that super hero mask on the general's head, you can clearly see in the shot the shadow of Aces fingers on the wall behind the general but not on the general's head.
When Ace lures the 2 poachers guarding the bat away by making gorilla calls, one of them identifies the calls as being a female "Silverback" Gorilla. The term Silverback doesn't refer to any specific breed of Gorilla and more importantly it would never be female as the trait only appears in male gorillas once they reach breeding age.
When the warrior rips the spears out of Ace's legs, you can see the Wachootoo Chief and the Witch doctor in the back round, but in the next shot, they are behind Ace, ready to pick him up off the ground.
When Ace breaks off the wheel handle attempting to escape from the Rino, you can see that it breaks off the base cleanly. When the camera angle changes, right before he throws down the handle, you can see that the base is still attached to the handle and there is an empty spot on the Rino wall where the base used to be.
When Ace is walking through a forest, there is a closeup shot of him saying "I can feel it like it's right...In my neck!" during that shot, you can see that the back round has clearly changed. (This is more noticeable on the 4:3 open matte version)
While driving through the jungle Ace hits a branch that breaks the car's windshield. In subsequent shots the windshield is clearly not broken. When they finally emerge from the jungle the windshield is cracked again, but in a pattern different from the first shot of its being broken.
When the 'stuffed' elephant head falls off the wall, its trunk breaks revealing it to be hollow and thus fake.
After Ace removes the apple from the victim's mouth, there is a shot where the victim and the medicine doctor are in the background. In the previous scene, the medicine doctor took out the victim's heart, creating a hole. However, in the shot with the victim and medicine doctor in the background, there is no hole in the victim's abdomen.