@PatchyFog My Kasa 3-way switch is now working in a 4-way configuration. The 4-way switches are irrelevant, and don't cause a problem. My problem was that my wiring configuration is different that...

@PatchyFog 'I am assuming the Kasa switches do NOT do any current sensing and must infer load (on/off) state from the switch "position"' It would be nice if KASA would give a definitive answer to...