In the very fast wide shot of Fremont getting ready to shoot Johnny’s drawing hand, there is no horse next to his uncle. After Lucas wounds the uncle in the shoulder, though, he slumps against the corral and his horse is there next to him, outside the corral. (That dark area by Freemont’s head is the horse’s front quarter.)
At the very end, it looks like one of the corral board’s ends has partially separated from the post.
Thanks Ann Marie for this page of bloopers!