The slip-up starts in the scene where the little kid (called Alex, I think) puts on the scorpion bracelet. He is shown putting the bracelet on his right wrist. He sees the vision through the bracelet, and then realises he cannot take it off until he reaches the temple. Then, you can see that every other scene in the film shows him with the scorpion bracelet on his left wrist. I am quite sure that if he could not take it off, it would not have been too easy for him to change which wrist it was on. A classic mistake in any film.