Audio problem: After Dutch has fired the rocket at the Predator standing on the log, the Predator shoots several times. Then you can hear it shoot one more time, but you can't see any blast coming from it. (01:24:35)
Audio problem: When Anna hits Poncho and takes off running, Arnie "whistles" at Hawkins with his mouth closed and the camera is looking directly at him when it happens. (00:41:05)
Suggested correction: The whistle is a tongue whistle. The tongue is curved via the teeth and the lips need to be almost closed to make the air rush out in that manner. It's sharper than a regular whistle due to this.
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.