Hi Caper and welcome. I had a router either like it or the same and I believe it was only meant to be used in the upright position. The ring would raise or lower it in that position but there was nothing to stop the motor from falling out of the base when turned upside down if I remember correctly. If you are using the the small Sears table that it was meant to fit into then try turning it on it's side when you adjust.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.