Revealing mistake: During the film's climactic end scene, just before the dentist wagon Potter and Jane used to escape the Indian camp blows up, the two protagonists jump off the released horse team to take cover behind a tree trunk on the ground. In that instance, you can briefly see the tall frame and definitely male face of the stuntman playing Jane's part in the scene. (01:30:50)
Revealing mistake: When Potter starts shaving at the morning of the Indian attack on the wagon train, his mirror falls off the post, and as he bends down to retrieve it, an arrow embeds itself right above his head. If you look closely in that scene, you can see a length of targeting wire used to guide the arrow sticking to the post above Potter's head. (00:37:10)