I recently took a loan of an additional A12 back with a view to purchasing it to supplement my existing back. It is in great cosmetic shape and seems to have been used sparingly and with care. However, when I am loading film in the usual way it does not stop at frame 1 like my existing back, it continues to wind the film onto the empty reel unhindered. It is older than the back I have been using. Is this a feature of the older backs (serial no. UC) or is it a fault? Regards, CT.