When the sheriff lassos Shorty, the rope is around his arms and torso; in the next shot, it's under the arms; then back again in the next.
When Katie shot the cigar in Barney's mouth, the bullet should have gone through the window in the door behind, but did not.
Barney Turlock, the villain du jour, is supposedly Billy the Kid's cousin. Billy was orphaned at a young age, assumed the surname Bonney, and had no known uncles or cousins.
When Katie shoots at the plates, she fires her gun three times but only two shots are heard.