On my camera, I repaired this by some judicious bending of the lever to get it to raise the stacked gear mechanism. The fault is caused by wear in the sprung lever which prevents it from lifting the pin far enough. The shutter jams partly open As per the following illustration, which shows the view from the back of the camera: This can be caused by damage to a sprung clip on the lower stacked gear, which interacts with a toothed cam on the upper toothed gear. This sprung clip holds the stacked gears together when the shutter is advanced. It is then pulled clear so that the stacked gears can run off individually to give the select speed. Illustrations next page