I've run into the same problem, the first one I ordered wouldn't work at all and the replacement wasn't much better. I think they all come from china. I would suggest trying to rebuild an original. If your patient, you can take them apart and file new stops and peen the shafts to tighten them up. Hit the swap meets and maybe you can find something better than what you got. Last resort just check with the venders and see if they will bench test one before they ship it to you. Just my 2$.