Other mistake: The catapult on the battlements Jean uses to evict the castle guards is rather curious. First, there is neither a bow nor any torsion to 'power' the weapon, and secondly it just seems to cock itself, right after each shot. All that Jean does is pull the lever and none of her diminutive helpers stand by for any cocking work whenever the catapult arm is shown.
Other mistake: Before the joust, Griselda tells Hawkins that she has put a pellet of poison in the vessel with the pestle; the chalice from the palace remains unpoisoned. Later, she tells him that the chalice has been broken, and replaced with a flagon with the dragon, in which she has put a pellet of poison. Both cups are poisoned.
Suggested correction: That might be a deliberate joke by the filmmakers, a reflection of just how far the confusion had gone.