Character opens eyes twice during scene, even though he's supposed to be frozen.
At the very beginning as Jim and Artemus ride into town there are modern tyre marks in the dusty ground.
After Jim places the second peg in the wall, the holes are visible for the ones going up.
When James breaks into the lab and sees Dr. Kirby face to face for the first time, there is a sudden shock of recognition between them. James confidently removes the doctor's toupee. Then the doctor vehemently sweeps off his own mustache and goatee. But there is no explanation given for this recognition.