I used to have a shuffle alley that would do the same thing. It had a hinged back door with wiring loom attached. Over the years the constant flexing of the loom near the door edge caused some wiring insulation to fray. When the door closed a couple bares spots in the wiring would touch. Sounds like what your on to but don't dismiss any wiring deeper in the loom. You may need to inspect a by spreading more of the loom to see if there are any more frayed wires hidden inside.