I picked up a Mamiya 127mm lens in a camera package along with a 90mm, and the 127 has a little problem. The shutter speeds seem accurate, the aperature is snappy, but the shutter is slow to fire. Meaning, when it fires it's nice and snappy but about a half second after it's been tripped. The 90 is perfect so it isn't the body, and it even does it off the camera when tripping it manually with the pins behind the lens mount. Any ideas???