My elderly mother lives, alone, in a townhouse (basement, full first floor, second floor "loft" type arrangement) in the United States. Construction date unknown, but probably 1990s.
She has twice experienced what I describe as a partial and temporary loss of electrical power: Electricity went out in some or all of the top floor, but (she swears up and down) stayed on for the main floor, and eventually returned on its own some minutes later. (This is an intermittent, not a persistent issue. We're uncertain what is causing it except speculation about a treadmill listed below. We can't cause the issue on demand and it does not last long enough for me to drive 45 minutes to check it out.)
This is not consistent with a local/neighborhood power loss because of the partial nature of it. I am not aware of, and the breaker box does not seem to support, and weird dual feeds, there's just one 100 A main breaker for the house.
This is not consistent with tripping a normal breaker because she did not reset the breaker. I would know, I would have to walk her through that process; and I looked at the breaker box this afternoon and everything appeared normal.
There is no generator or other back-up power supply, much less one that only works in certain rooms.
The only recent change is the movement of a treadmill (which never goes faster than the lowest setting of about 1 mph) from the basement to the room she was in; the treadmill was in use both times. The treadmill outlet is not GCFI.
There are only two situations I can think of here:
I am aware that self-resetting breakers exist. I'm not sure if they would ever be considered up to code for a residential building, or if they look any different from a normal breaker. (This is farfetched, to say the least. But my father, before he passed, was a licensed union electrician for 40 years. He never mentioned doing anything like that, but if it would be up to code, it is at least theoretically possible. I would stake my life on the fact that he would never do anything not up to code anywhere, much less his own house.)
A loose wire somewhere on the circuit, probably where the treadmill is plugged in which is getting knocked out of position either due to the vibrations of the treadmill or thermal cycling from the new current draw. Either of which would be very bad.
Am I missing some other possibility?
(In fact, the real subtext of the question is, "Do I need to get an electrician out there Monday morning to hunt for the loose wire/fire hazard?" But that's not a good title for a question.)
PS - The treadmill is off-limits until this is sorted out.