I have a series E 50/1.8 that doesnt stay wide open for metering, if I take it off the body I can move the little lever on the back and it works like it should except that if I'm not careful it depresses into the lens body. I think this is what happens on the camera. It's a junk lens, big cleaning mark on front element, that I use as a body cap on bodies that I'm not using at the moment and probably not worth repairing. just wanted to know if there is something that I can do to fix it. I'm mechanicaly inclined but dont have the proper tools or any idea of the inner workings of the lens