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 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.