OK, so, I think Simon was on to something. Here's what happened to me. My back wheel had the bolt unscrewed so long and I rode it so long with it like that, that the bolt starts to file away at the hole in the deck until it is much bigger. Then even when your bolt is tightened it can still move around because of the bigger hole in the deck. That has happened to mine and maybe that bigger bolt thing would work but it would still have to fit into the socket of the whatever goes through the back wheel. Hope it helps.