Jonieelvis and original poster-- the realist 45 is not like other stereo realist cameras, which were made in USA and have a single metal guillitine shutter and are fairly simple to service. The 45 is German-made, really an Iloca, with two separate blade shutters which are linked, but are not the same as what you describe. If one is a bit sticky and slow, it will definitely give you differing exposures.
Time for a CLA, although for the price you can probably find a more traditional Realist camera, the boxy-looking predecessor to the 45 which jonieelvis is thinking of. That camera will be more durable, have a built-in rangefinder with no parallax, and be funkier to use. The Realist 3.5 models in usable condition usually run $100 or so. Those with the 2.8 lens cost more, but are no better, image-wise, and for stereo you want smaller aperture anyway.
here's a good description of the basic models http://en.wikipedia.org/wiki/Stereo_Realist
Last edited by summicron1; 06-17-2013 at 12:28 AM. Click to view previous post history.