As far as I could tell, the shaft was fine. It was the inside of the pulley that was the softer metal and had worn away. I believe that the design defect is making the "socket" larger than the shaft. When the bolt inevitably loosens, the pulley starts banging around. I was hearing that banging noise for months, which gave it plenty of time to wear down. There should have been a plastic or rubber bushing that prevents play, or the bolt should have come in through the side. In any case, make sure you use thread lock. Mine is still fine.