After the rattlesnake causes the horses to bolt, Lucas jumps onto the wagon in an attempt to stop them. When the dummy that's supposed to be Lucas falls off of the wagon, it comes to a stop near where it fell off. But in the next scene, you see Lucas rolling down the hill where he crashes into the rock.
Lucas places the water barrel onto the wagon but when the horses get spooked by the snake and start to run, the barrel is back on the ground as if Lucas hadn't lifted it yet.
In scene in desert while Lucas is climbing, his back-end is showing.
He is wearing denim jeans.
The stitching on back pocket is a W.
That's wrangler brand.
Wrangler wasn't around until 20th century.
When Mark sets out alone in the desert he finally stops on a double tree and sits down to drink. Much later he stops again for a drink and apparently sits on the exact same tree.