Shiro Tanaka lost his crossbow to the natives when his rope breaks crossing the waterfall gorge. They pick it up and shake it at him as though taunting him. Immediately afterward, he is shown once again with the crossbow slung on his back. Then it's gone again in the next shot.
When the natives shoot arrows at Shiro Tanaka as he crosses the waterfall gorge on a rope, an arrow supposedly gets shot through the rope at right angles. But they are shooting almost directly straight along the rope at him, so that would be impossible.
When the arrow is shot into the rope ahead of Shiro Tanaka, several views of the rope and arrow and Shiro Tanaka in the same frame show the arrow is actually tied to the rope on the side away from the camera. Then in closeup it is suddenly sticking through the rope and the rope is cut and breaking.