I have a Mamiya 645 for about 9-10 months now and enjoy the feel of the camera. I welcome change from my Kiev 88cm with my many ultra leaky backs (only objection to that camera). My problem with the 645 is a sometimes stiff trigger. It causes me to jerk the camera slightly. Just enough to lose sharpness. What I don't understand is sometimes the trigger is quite smooth. I also have a motorwind unit for it and it suffers the same fate. I was hoping the the consistent trigger motion would solve this. Is there actually something wrong / worn? Is there an adjustment or something I can do?