Near the beginning when Roy is buried up to his neck and the vultures are picking at his head, the "Shanghai Kid" shoos the vultures away and steps in the way of Roy's view of the sun. When the camera is set back on Roy there is no shadow on him.
There is a very small shadow, but its shifted and is in a different direction, as if the sun had moved. Which clearly it wouldn't have had time to do naturally: it just means they did different shots at different times of the tame. A perfectly good slip-up.
I saw that too...notice there is also a shadow to the left of Roy's head, and of Roy's head, this would imply the sun was beating down on the right of his face...not in front of him...2 suns?