Joe. I've never even seen one. In the flesh, that is. If it tends to stick in certain places it may well have suffered a blow sufficient to get it a hair out of round.
I was de-yellowing a Super Takumar 50/1.4 for a friend from Ontario (not much sun in Oslawa). Had it perched on a fence facing south and wrapped in foil and kept in place by well-placed stones. Unfortunately it was too near the gate and a huge surge of wind slammed shut the gate and dislodged the lens. It fell about four feet onto soft earth, except for a small rock lying there. You could see where the stone had impacted the aperture ring. Barely, that is. Took a magnifying glass. Sure enough, a bright aluminum spot where the black paint had been chipped away. The aperture ring no longer moved smoothly throughout its range, hung up rather stiffly at f:2 and 3.5, exactly at the point of impact.
Had to send it off for a new ring. Solved the problem.
Then there's always a tiny drop of watchmakers oil...
