Just picked up a couple of very clean DC07s for nothing - happy days. However, one of these is displaying a strange fault. The motor runs well (although accompanied by a slight burning smell), and the cleaner picks up dust well. On switching off, there is a loud, rough clattering noise, which goes on for about 20 seconds after all power has been disconnected. I haven't had the chance to strip the cleaner yet, and suspect that I may be looking at a new motor. Has anyone else come across this? It just seems very odd that this happens when the vac has been completely isolated from the mains!