Mamiya 6--shutter activates after 12 frames?

[katgut@earthlink.net]

My Mamiya 6 (first modern version) doesn't seem to function properly. After taking 12 frames, I still have to fire the shutter to wind the most of the end of the film. It will usually go to 16 frames before it free winds. I was under the impression that after 12 frames it should automatically free wind the end of the film. I did check the pressure plate position, and the tiny lever that changes position and transmits the roll size info to the body seems to be in the right place. Anything else to check?
thanks

 

[jbh]

It's not supposed to work that way; it should free-wind after 12.