Ignoramus25009 wrote:
Seems consistent with the possibility of a thermal overload
somewhere...

Just trying to wrap my brain around the concept:

Say there is such a thing as an overload cutout which opens one of the
two hots.

Say you have a largish 240V motor or oven connected between the two
hots.

Won't many of the (low current) devices on the opened circuit see
lower-than-normal-to-normal voltage through the motor?

Sounds like a bad idea. I know that after you get past the breaker box,
any circuits that share a neutral must have breakers that open both
poles.

Of course, all sorts of bad things can happen between the power pole
transformer and the entrance panel, for example having the neutral go
open!

Tim.