I recently acquired my first Hasselblad. A 503 CW overhauled by Hasselblad, along with the lens and film back. I am at the stage where I'm trying to familiarize my self with my 'bald. I did the adjustment on the lens and the body coupling screws. I found a fine B60 UV for my 50 F4 CLE. All fine the camera was cranking without a problem, release button working smooth. Today I find that I cannot wind the crank, if I remove the back the crank, mirror, shutter all work. I put the back on in place, I cannot wind the camera. Are their persons familiar with Hassy and what I described. Your help is solicited.