I've been bothered by these light leaks ever since I started using this Mamiya RZ67. Please see gallery here:
http://imgur.com/a/URxVz#0Originally I thought the problem was one particular back, but the problem seems to exist across at least two different backs. Even worse, it's occurring intermittently across rolls of film. Some frames are fine, some have this very faint strip of discolouration either across the top, left or right sides.
I've tried the standard method of checking the bellows for cracks or light leaks and it seems fine. I will try changing the light seals on the backs when I can get new ones, but I have a sinking suspicion the problem may be something less straightforward, as the leaks change position from left to right, or top (and also bottom in example #3). Also, shouldn't light leaks bleach the film rather than darken it?
Before you suggest that it's a development issue, my lab is a fairly professional film lab, and I have dropped off rolls shot with my Contax 645 at the same time as ones shot with the Mamiya, and the Contax rolls are fine.
Can anyone offer wisdom on what might be causing this problem?