Gen 1 Contact Sensor Factory Reset

After following the instructions for the factory reset of a Contact Sensor Gen 1 and failing miserably, my curiosity eventually found a solution. Ignore the official Ring advice, it's incorrect.  With the cover still on the device, perform a factory reset by inserting a paperclip into the reset hole on the back of the sensor and keep in place.  (Yes - just like the Gen 2 instructions).  This will trigger the reset routine and the blue light will flicker away as it should do.