Revealing mistake: In the final Indian chase at the conclusion of the film, when a covered wagon rolls over, one can see the rope that was used to ensure it tipped over.
Revealing mistake: Near the beginning, when the giant fiery comet hits, it goes behind a hill, yet you can still see the glow of the comet through the hill and the shops in front of the hill, revealing it is a backdrop. (00:04:20)
Revealing mistake: In the scene where Lancelot runs into and fights Arthur's ambushers, he runs one of them through with his sword. It is visible that he stabs his opponent past the body, but close enough for the appearance.