Revealing mistake: When Crockett, Bowie and their men are about to destroy the giant cannon, several of the men are standing right next to it at the moment one of them tosses the torch on the touch hole. Then, there's a big flash at the touchhole. In the very next shot, right before the cannon explodes, we see the cannon, but everyone has disappeared. There was no time for them to flee completely out of sight.
Revealing mistake: During the initial breakout of the Gladiatorial training school an armed guard is stabbed on a balcony and falls to the arena below. He gets up and walks into the doorway adjacent to where he had fallen, apparently satisfied that his part was completed.