Revealing mistake: In one of the flashback scenes at the "bunker", a number of the shots fired pierce the sheet metal roof. When they show these holes, you can see fairly bright light coming through. This scene was supposed to be in the jungle during the night. There shouldn't be light streaming in; moonlight is not that bright. It was obviously artificial light used to enhance the scene.
Revealing mistake: There is a scene where Travolta is holding a prisoner up to a spinning airplane propeller to force him to reveal information. This is supposedly taking place in a pouring rainstorm. But during one of the close-ups, you can see that no rain is falling on Travolta's jacket. The jacket is wet, but no raindrops are falling on it.
Revealing mistake: During one of the flashbacks, Dunbar goes to shoot Mueller in the head, but Mueller wakes up suddenly and pulls the gun away from his head causing the gun to go off and shoot a guy in the back. Now in this shot just before we see the blood, look closely at the guys back, and you can see the device/squib in his back simulating being shot in the back. (00:40:30)The-Immortal