The hole is not threaded or otherwise exhibiting any signs of machining for any instrumentation or sensors. Attached is a closeup of the actual port. A little out of focus, but you can see the plug pushed out of place and what’s left of that washer. Since it’s orientation was directly on the top, I think it just retained moisture in that recessed hole and the star washer simply corroded away until I hit the brakes hard enough to “Phsst” it right outta there.
