I have had my Dyson for a long time and it has had this problem for a few years now.
After you empty the bin, the assembly may or may not snap back into place. Sometimes it goes back on on the first try, sometimes it takes several tries. I have even given up and left it unattached to fight with another time.
If I have more vacuuming to do, I can hold the bin place while turning the power on and the vacuum pressure will hold the bin in place, but you have to catch the bin after you turn the motor off.
Since this is intermittant, it of course works when I take it to the repair shop. I have spent a long time on the phone with cust service only to have them end up stumped.
I know that I can order new parts but nothing seems to need replacing. It vacuums fine without any strange smells or noises. Has anyone heard of this problem? My husband sees the only answer as buying a new one.
Thanks.