Hello, I recently acquired a Mamiya 645 Pro TL with the WG401 winder grip. I have noticed that the "winding sound" is inconsistent. Approximately 3 in 10 advances will sound short in duration, as if the film didn't wind completely to the next frame. Consequently, the frame rate is noticeably irregular when in continuous mode. And this is without film loaded. My concern is that the frame spacing will be uneven, but I haven't run a test roll yet. I've tried changing batteries. Also, there is a pin on the back of the body, top right corner next to the shutter. http://youtu.be/D2W301xUBSY In this video (skip to 3:43) the pin pops out and then quickly retracts after each exposure. But with my camera, the pin does not retract half of the time. Should I be worried about this? Could this be related to the frame rate problem? One more question: Is it normal for the winding action with the hand crank to feel like I'm breaking something? After 3 quarters of a turn there is a CRACK sound and some resistance and then no resistance at all for the rest of the action. With the Hasselblad the movement is smooth throughout, with constant resistance. Any information would be greatly appreciated - I don't know too much about the Mamiyas. Thank you!