During the opening scene when Bronson's rowdies tear up the town of Bannock, in two views of the local hotel, the town's name is spelled Bannock. Later, when Sheriff Maddox checks into the hotel in Sabbath, he signs in as a resident of Bannach.
When Vernon Adams (Robert Duvall) first aims down on Maddox (Burt Lancaster) with his rifle from above, Maddox is riding away from him up a long draw. Immediately afterward, Maddox is still traveling up the draw and looks up and sees Vernon in front of him and above him aiming down at him. The positions switched 180 degrees.
When Maddox (Burt Lancaster) shoots the horse out from under Vernon Adams (Robert Duvall), the man who is thrown from the falling horse has a full head of hair, and is clearly a stunt double. Robert Duvall was totally bald on top in this movie. The stuntman even tries to hide the fact by placing his hand right on top of his head as he comes up, but the full head of hair is still visible.