Sometimes when I mount my 45mm, it does not stop down. Meaning, if I dial in F/2.8, the photo ends up 1.3 stops overexposed with the DoF of F/1.8. If I dial in F/4, the photo ends up 2.3 stops overexposed with the DoF of F/1.8. But if I dial in F/1.8, it's fine. If I compose a shot which meters neutral at F/1.8 1/200th and 200 ISO, but then dial in F/16 1/200th 200 ISO, I get a neutral exposure. Logically, I think the aperture blades aren't moving. I don't think it's "sticky aperture blades", because it only happens sometimes, and if I dismount/remount the lens, or sometimes just reboot the camera, it fixes itself. Has anyone seen this? I've experienced it on 2 E-M5 bodies, and none of my other lenses have this problem. I really haven't used this lens that much, and it certainly hasn't experienced any trauma.