200K on the clock, the first thing I would do is check the electrical portion of the ignition switch, is there is a problem with that it could easily manifest itself as "electrical ghosting" like this.

And that could be pretty quickly and easily diagnosed or eliminated by swapping some other electrical switch into place of the original, even and unknown used switch is highly unlikely to have the exact same specific flaw so any change from the present state of that light illuminated would confirm the original switch as the source of the problem.