When Lucas is saddling up his horse Razor to go into town, Mark is sitting on the fence stroking Razor's face. The next shot is a close-up of "Razor", but it's an entirely different horse than the one Lucas is saddling.
When Haskins is bitten by the horse, a close-up of his arm shows it covered by a dark long-sleeve shirt. Before the close-up, Haskins was wearing a light-colored long-sleeve shirt with a coat.
Mark is given an anthrax vaccine, but the human anthrax vaccine was not available until 1954.
About 5 minutes into the show, a shadow of equipment is seen on a post just as Lucas and Mark ride off with 'The Pet' roped to the back of the wagon.
When Lucas and Haskins are fighting in the barn, Haskins runs away from Lucas towards a window. An obvious stuntman as Haskins had little hair and the stuntman had a full head of hair.