Having recently bought a second hand Olympus 75 f1.8, I think I may have noticed a possible issue with the aperture blades, possibly sticking, but I'm uncertain and seek your advice please. I've noticed a clicking sound now and then, and when I look I can see the blades in a partially closed position. But pressing the release button half way, the blades fully open, but return to their partially closed position when the shutter button is released. Switching the camera off and on clears the 'apparent' fault, but it does return periodically. Any ideas, anything I can do to help diagnose the problem. I've not seen this with any other m4/3 lens I own. Cheers.