It's funny that this thread was brought back from the dead right now, because I just bought an ME Super from an antique shop, shot a roll of film with it that turned out great, and 5 minutes ago I went to load another roll of film in it and the film advance lever did this exact thing.
There must be a connection or pin broken because it'll click in and out of it's "totally shut / slightly unshut" positions, but open it past those two clickable positions and it swings freely. Clearly there is no connection, no grinding or broken gears, it's like spinning an office chair.
Bummed me out because it's $40 down the drain and it was in really good condition too. Now I've got a dead ME Super, dead K1000, and working ME with no light seals.