Can you return it? It sounds like somebody must have known about that one. I have no idea how to fix that. If it were vintage, I would take off the clamp and look it over - if it was ok I'd put it back on - if not I'd pull one off a junker - if it takes a regular screw you might be able to find one on line somewhere. If I had that machine and had only $20 in it I'd take the whole thing apart just to see how it works. LOL
actually, I've done that - My sister and I bought a plastic machine just to take it apart - we did get it going after a couple hours but we never liked it.