I have the EXACT same problem. In fact, it is funny all of the problems I have seen listed on this page, because it seems my MX-6 is prone to them all.
Anyway, mine would start to slow down and stop moving sometimes YEARS ago (bought my 94 brand new, now has 108K on it.) I greased it and it got a little better, but it does it all of the time now. I generally use my hand and assist it when it closes. Sometimes it closes but it is a little off... It closes with a snap sound and is not perfectly seated. I then have to open it and close it again. Not much of a 'fix', but that's what I do.