my assylum upkicker always seems to make a metalic clunk when a ball goes in and a lot of the times when it comes out. there is a rubber stop at the bottom for the plunger to rest on. the ball hits the sides of the scoop and makes a clunl going in and I think it hits the scoop on the way out and clunks sometimes. is this normal and if it is not how would I adjust it to remove the clunk