I picked up a brand new set of these ratchets about a year ago pretty cheap. The grease in them had about dried up and hardened so much it made the ratchet mechanism stay engaged all the time and it couldn't be reversed. I guess thats about the opposite of the problem your having, but at least it didn't make me bust my knuckles!
I opened them up, cleaned and regreased, and reassembled. In reassembling, I found that the adjustment of the hex bolt in the middle is ultra-critical. When it is just right the ratchet is perfect, but when it is just a hair too tight or too loose it will drive you f&(%!^g nuts. I found that it worked better if I removed the large central washer that supposedly allows you to apply palm pressure on the ratchet head. I replaced it with a flat washer & it worked better. I no longer have the option of applying palm pressure, but that never worked very good anyway.
I usually use my old SK Waynes anyway, so these usually just lay in the toolbox drawer taking up space. Maybe I'll sell them at the flea market.