On the passenger side my wife constantly has to put the constituent elements back together as we're out and about. I need to find out why it happens. That's the side I had the bad accident on back in 2014 so it could be related. I'm sure in a box of bits I've got spares so will have to see what I can do. For the base I'm thinking broken, weak spring behind the cover or a worn loose fixing pin and for the top part, just worn parts. Mind you I can't see how they magically stay together anyway. It's devil's magic!