Continuity mistake: When Mac first shoots up the jungle, he runs out of ammo. From the behind shot the barrel of the mini gun isn't spinning. Then, from the front shot when Mac releases it the barrel is spinning. (01:46:25 - 02:46:30)
Continuity mistake: When Mac calls to Dillon about the scorpion you can see that there wasn't one on his back to begin with.
Continuity mistake: The bullet riddled tree that Poncho is hiding behind changes. It goes from severely riddled to not as much damage.
Audio problem: While a cool sound for the movie, the electric motor powering the M134 mini-gun vastly overpowers the sound of the actual gunshots from it, essentially making it sound like a turbine engine instead of machine gun. Plenty of videos available show this is impossible.
Answer: In the shots where we can see what the Predator sees, sometimes when he is focusing on someone or something, we hear a kind of flash noise as he zooms in on the object. When we see the Predator's eyes flashing/glowing, that is when he is zooming in on what he's looking at.
dan coakley..