I recently got this adapter to mount my Hasselblad 50/4 Distagon C version lens on my Nikon D750 - FotodioX Pro Lens Mount Adapter for Hasselblad V HBV-NIKF-PRO The first hour or so seemed good - shooting wide open or using the DOF preview lever to stop down and shoot (then opening up aperture blades by switching the lens to wide open at f4). However it randomly jams (the lens shutter blades suddenly close and can't be released again with aperture ring or DOF lever). There doesn't seem to be a pattern to when or how. When it happens, I have to wind the lock on the lens to re open the aperture blades as per this video - It's happened a few times already in the course of one day. Do you think the problem is the adapter? Or the lens? Or something about my technique?