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: Though the loose ferris wheel keeps rolling for over a mile, the guys seated on it remain in the same position all the time instead of rolling down and getting crushed by it. Furthermore, they disappear in the wide shots and the wheel appears empty.