3 way switches

[BarryO]

But it is an unavoidable aspect of the physics of the situation that there will be _some_ current on the EGC because of leakage and capacitive coupling. No insulation is perfect and even if it were there is still going to be capacitive coupling.

And there can be intentional capacitive coupling as well. EMI filters commonly have line-to-ground and neutral-to-ground capacitors, which may put a few 10ths of milliamps on the ground conductor at 60 Hz.