I was swapping out a basic Honeywell thermostat for a smart one, and the thing kept showing no power even though the breaker was on. Turned out there was a stray voltage leak from a shared neutral in the junction box, something the old unit just ignored. 4 hours of meter work and cussing later, I found a loose wire nut in the attic that was barely touching. Has anyone else run into phantom voltage messing with their low voltage stuff?