This slip-up is located in the last fifteen minutes of the movie. All of the stones are in Corbin's possession. The whole crew are in the temple in Egypt. The priest explains that the stones go 'round and then the weapon is opened. He picks up one of the stones and says that it is fire. However, that stone isn't fire. It is either water or air. the fire stone has wavy lines going from the bottom toward the top. When they go to the next scene the stone is actually the fire stone.

This slip-up just jumped out at me.