A prop that only moves very slightly a short distance is telling you something.

The perfectly balanced prop won't move at all when placed at any position. And obviously won't move no matter what that position is.

If the prop moves only very slowly and only a short distance, it's very close to perfectly balanced. And if that's somewhat random, you have an imperfect balancer.

I would suggest that your balancer is not perfectly free of friction, or the prop isn't being held uniformly or not securely.

and.........................