[mr rusty]

It is a shutter fault

No its not.

It's light leaking in around the catch for the back door. This exposes a strip of the film exactly as shown. I know this because I had exactly the same. I replaced the back door foams on my new-to-me M645J and stopped the foam strips just either side of the catch, figuring the bit of metal on the back door over the catch mechanism was a light trap - wrong!. First film I shot was OK - prob because I shot it over a short period of time in subdued light. Next film I was carrying the camera around in sunlight and ended up with exactly this strip across the neg. I bet if you look at the neg itself the dark stripe extends beyond the exposed area to the edge of the film. I re-made the seal making sure the foam was continuous around the catch. Get your seals sorted and all will be good.

lightleak.jpg

quick scan of top of offending neg

Light seal kit here http://www.ebay.co.uk/itm/LIGHT-SEAL...item589ac410c8

Good tip when using self-adhesive foam - wet the surface of the sticky surface with a small amount of water with some wetting agent - detergent or photo flo - you don't need much. The self adhesive foam doesn't stick at first and you can easily slide it about. leave it to dry and the foam is then stuck properly. Trying to do mirror foams, where you have some awkward positioning, without knowing this trick is almost impossible because dry, the foam sticks straight away and you can't reposition it