Mine works pretty good after I got the "hang of it". Generally I bring it all the way up to the "top" position before letting it down to the desired height. IIRC...........that's what I've been doing to my satisfaction. But mine was bought brand new in 2012 and is well broken in.....maybe that has something to do with it. I assume the engine is running and hydraulics is okay.
BTW..........edit........the "setting" can change positions as one mows. I'm guessing that some bumpy knocks can throw it off. I usually keep an eye on it as I mow along..
Cheers,
Mike