MiamiCuse wrote:
....

I examined the wires in that box closely, and I did not see any exposed
copper at all, which is troubling. What is even more troubling is that
there is no wire that is charred, only the box.
....

I wouldn't expect "charring" from a momentary arcing but there's
definitely something in the vicinity that could have touched at the
point indicated on the box.

Not being able to see it, no real specific ideas but is it possible the
electrician was carrying something (like a roll of wire) and it brushed
a hot point rather than it being the wire in the box at all?

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