Other mistake: Early in the film Wayne and others have two steers tied, lying on their sides for branding when they are approached by Mexicans. Following a dispute Wayne kills one of them,a grave is dug and a brief service is held. Following this (which must have taken at least a half-hour) the same cows are still tied up; it is doubtful that a competent cowboy would have allowed them to be tied in that position for that long.
Other mistake: When Abbott and Costello are bringing the first crate (Dracula) into the house of horrors, Abbott tells Costello twice to help with moving the crate. The first time Abbott says to help pull the crate, which is correct. The second time, Abbott says to help push, even though Costello is still pulling.
Other mistake: When Jack Warner puts on the Corporal's uniform how is that possible when he's handcuffed to George Cole? (00:16:00)
Other mistake: Brandon is wearing gloves but Phillip is not when they kill David. Afterwards, Brandon removes gloves from Phillip's hands.
Other mistake: When Bob Hope is singing Buttons and Bows with accordion, to a sleepy Jane Russell, no-one is driving the horses.
Other mistake: When the old man was resuscitating the unconscious boy he kept his arm sticking up in the air. His arm should have been besides his body, limp and unmoving.
Other mistake: When Sam tries to bring Bugs down from the crows' nest/elevator, he pushes the "Up" button and brings it down.