Fuji GX680III repair

Hi all,

I've got a Fuji GX680III that flashes the warning triangle when I power it up. The manuals I've read seem to say that this indicates a problem with connections to the lens or film back but in my quest to trace the leads back to the electronics I've run into a wall. How do I remove the two large brass screw caps that hold on the lens rails? The cap slots are wide and thin so regular screwdrivers will gouge the soft brass. I tried shaving down a dime to fit but it just bent it. Or do I even need to remove the rails to access the electronics box?

Also, does anyone have any pinout information for the connections?

Thanks,
Brian