I don't know what model or vintage you have but several years ago I had a somewhat similar problem. I called Hasselblad and was lucky to speak with a technician who immediately knew what the problem was. I sent it in and it was repaired and has worked well since. As I recall he said it was a cam(?) and they had re-designed or were making them of a new material. You might give them a call or check with one of the repairmen often mentioned on the forum.