I don't know of anything else that would cause it to break. It's a pretty simple straight forward design, ya know. It's either gotta be wallowed out, or wrong key. The parts should slide together very snuggly. You might also check the shaft. If it has spun on the shaft to much, it might have ground it down a little, putting all the pressure on the key. Leave the key out, slide the parts together. If there's any play there at all, or if the parts slide together too easily, the shaft might be ground down a little. If you lived close enough, i'd help ya out with it..........