Revealing mistake: Near the end, when the captain is walking out of the labyrinth holding the baby, you can tell it's a dummy. The baby does not move in the slightest, you can't even see it breathe.
Revealing mistake: The wound to the captain's mouth disappears when he walks out of the labyrinth holding the baby, towards the end of the film. As he is talking to the soldiers the dressing on his face moves showing no cut underneath.
Revealing mistake: When Ofelia is giving the mandrake two drops of blood, you can see that she is squeezing a clear tube between her fingers. (01:05:51)
Answer: I saw nothing in the movie indicating that. Ofelia's task seemed to be to retrieve the blade, she failed because she didn't follow Pan's instructions about not touching the food.
Andreas[DK]