Deliberate mistake: Martin Sheen has a cut on his cheek that starts as a scar and becomes an open wound. (00:02:27)
Deliberate mistake: None of the helicopter's in the movie have the Army markings seen on Vietnam era Hueys. The most you'll see is some crooked, faint and inaccurate stencils in the wrong spots. (00:37:50 - 00:51:25)
Deliberate mistake: After Hubert exit's the French Plantation dinner scene the stage lighting on Roxanne and Captain Willard shuts down abruptly before their close-ups. There's no one there to touch a light switch and we can see outside and the natural lighting hasn't changed. (02:13:30)
Answer: It should be noted that "transmutation" is a word Coppola has used to describe the film making process. Https://m.youtube.com/watch?v=LFTQcwgq4CY.
Bishop73