My Bronica ETRS has developed a strange issue. The battery is known good/new, and the camera did work well. However, now about 80% of the time when depressing the shutter trip button, the mirror will raise but the shutter will not fire. Very slightly moving the lens will cause the shutter to fire for the correct time specified. Should I get a new lens? The contacts look clean, I have yet to try and clean them better. At this point because all mechanical devices seem to work, I am leaning strongly towards an electronic fault. Any thoughts? Thanks.