Continuity mistake: After Chef looks over the papers handed to him by the people on the Vietnamese sampan, he hands them to Chief Phillips, who puts them under a brown flak jacket tied around a metal roof pole on his left. This brown flak jacket appears, then disappears between shots.
Audio problem: On the French plantation dock Captain Willard walks over towards the Frenchman and they do an excellent job of overdubbing the sound of his helmet strap each time it hits his chest. Two shots later they don't put in the sound as the helmet strap hit's against his chest several more times.
Continuity mistake: In the rear close-up shot of the Vietnamese machine gun nest the soldier in the dark green shirt is to the right of the soldier in the tan shirt who is firing it. In the next shot the soldier in the dark green shirt is behind and to the left of the soldier in the tan shirt.
Continuity mistake: In the first close-up shot of the soldier wounded in the courtyard the medic behind him tries to give him some water as the camera pans away to two Vietnamese civilians for a second. In the next shot the medic is still holding the canteen but the injured soldier now has something hanging out of his mouth, that looks like a piece of string, which wasn't there in the previous shot.
Continuity mistake: As they stand on the French plantation dock we see the front of the boat a lot and the chipped paint from the rocket attack in the previous scene has been repaired. There's also a camouflage shirt under the radar dome that sometimes has a T-shirt next to it and sometimes doesn't.
Continuity mistake: The lights on the Do Lung Bridge keep changing between shots. There are many more burned out light bulbs in the shot of Captain Willard and Lance as they leave the boat then there are when we first see the bridge or when the bridge is in the background as they walk past it.