Director screw up

Why did the director not reshoot the scene at the end. The wizard was getting ready to leave and to to ran off. Dorothy jumps out and as the balloon starts to go up. You can see clearly the tin man unwinds the rope from the board. It drives me crazy every time I see it. He let's the balloon go and acts so disappointed when the wizard flys away. I know dang well everyone could not possibly miss the tin man unwinding the rope.

Just my thoughts

Lorie