When Haines arrives at Preston's ranch, he ties his horse securely to the hitching rail. When he leaves a minute later, he mounts his untied horse.
When the fuse on the dynamite is burning down, the length of the fuse remains the same between shots, despite time passing.
When the dwarfs play their musical instruments, the guy playing the cello gets the bow stuck in the strings and has to fight like mad to get it out, but the music continues.
When Otto the cook is trying to entice the duck to come closer, a shadow of the boom microphone is visible on the side of the barn and on the ground beside him.
When Buck Lawson stops the stage coach and then drives it away, he leaves his horse behind.