After I use a cap driver for about 2 dozen hats, I have to start putting shims between the clamp and the cap frame to keep it from becoming dislodged.

I thought my first machine's driver was a fluke. I just added a second one, and it's doing the exact same thing.

I have, therefore, concluded it is not a fluke, but is an operator-knowledge-deficit problem.

What do I do?