I've just acquired an MD-12 for my FM-2n. The issue is as follows: when mounted to the camera, the motor whirrs and the red LED comes on but it doesn't advance the film or release the shutter. I've done internet searches and have tested it by shorting the 4 pins. When I do this, the motor whirrs but the the film advance drive dog does not turn. The shutter release pin is retracted. Does anyone have a suggestion to get it going again?