When the Indians attach the stagecoach, a soldier is shown aiming his rifle, then it switches to him holding a pistol and shooting it, then right back to him holding the rifle.
When Chief Paako is talking, he frequently slips into a northeastern accent and the rapid and fluent way of speaking American English from early American movies and TV, without any hint of the 'Indian' accent and broken English that actors portraying Native Americans in old westerns typically used.
In the dance social scene, the guitar player is playing a 1940's model Gibson F-hole guitar.
When Ike Vaughn (Gig Young) flees the fort with young Nancy Dempster, he runs and jumps on his horse and rides out of the fort through the open gate, supposedly holding Nancy all the time with his left arm. But the action is rather violent, and from the way he holds Nancy, you can only see her back. But her arms and legs flop around like a rag doll, which is clearly a prop and not the real girl.