Every time I process a roll of 120 film the last three frames are always wiped out, looking like they've suffered massive light leaks and being completely ruined. I think this is a problem with my processing as whenever I have had a colour rol processed at the lab it comes back fine - my black and whites are the only problem. Does anybody know why this might be? Up until now I could live with it but as i'm about to do a wedding i'd hate to lose 3 shots per roll. Thanks very much.