I've had this issue a few times. Took it apart and soaked/scrubbed anything without a pcb or wires coming out of it, and it worked fine after. Eventually the filter on the motor crumbled into dust (not suitable for picking up the dust from sanding paint off indoor walls). I tried to get the right one from Dyson but I ended up just grabbing something that looked like a distant cousin of the right filter off eBay and cut it into the right shape. It stopped working again after a few months, I was going to do the cleansing ceremony again, but then I dropped it and it started working fine again.

Going on 13 years now I think.