Revealing mistake: When the GI's are jogging through the training camp complex, singing "I don't know but I've been told..." you can see the British road junction markings on the tarmac underneath them. There is little evidence to suggest that there was any attempt to disguise or remove them.
Revealing mistake: In the early latrine scene when Privates Cowboy and Joker are mopping the floor, the mops they are using are dry. As they dip each mop into the bucket, there is no water dripping. When they move the bucket, the sound indicates it is empty, as anyone who has ever used a mop & metal bucket could validate.
Revealing mistake: When Joker and Raptor are in the helo heading for the front, there is a view of Vietnamese being fired at by the door gunner with an M-60 machine gun. Several seconds pass in the scene while bullets should be tearing into the ground around them, but there are no indications of bullet strikes, even as the line of fire passes over a small creek.