I was out with my Mamiya RZ67 a few days ago taking some autumnal shots when the shutter in my 50 mm lens failed to close after making an exposure. This effectively 'bricked' the camera, which only responded after removing the battery for a minute or two and reinserting it, whereupon a faint click was heard from the shutter. It seems the leaf shutter mechanism in this lens has become sticky, as it works perfectly well in the warm at home, but stops working when it becomes cold. A change of battery made no difference, and my other lenses continue to work perfectly well in the same conditions. The lens is otherwise in perfect condition, with crystal clear optics, so I would be keen to get it repaired if possible. Does anyone have any recommendations? Could this even be a DIY job? I have previously used Johnson's Photopia for Mamiya repairs but they were very pricey, so I would like to find a good independent if possible.