I was working with an electrical engineer. He tells me the the Gieger counter isn't working. I flip the switch to "Bat", and I see it's low. I tell him to put in new batteries (2 D-Cell batteries). He puts in new batteries and then tells me it still doesn't work. I open up the battery hatch and put them in with the correct polarity and all is well. I guess I should have told him to put in new batteries correctly.
I wouldn't have remembered this for putting in the batteries backwards, because I've done it, but I took it one step further to realize the polarity was wrong right away. He wasn't much of a problem solver.
A good friend of mine was an RF engineer. Like, radios, signals, etc. Really high-falutin' stuff with brain-cramping calculus flying everywhere. Not to mention the stuff you're trying to control is invisible...
Anyway, he had a vintage motorcycle with the usual sketchy vintage wiring that was causing issues, and decided to rewire bits and pieces of the wiring harness. Simple plumbing, right?
Wires proliferated, multiplied, and the mess of spaghetti grew and grew until he couldn't get the side covers on any more. The issues with his bike continued and worsened. He had boxes with relays, terminal strips, connectors, etc. everywhere. Each bit of wire had a very complex theoretical reason for being there.
The bike got worse and worse, and finally refused to start at all. I went over to his house to ponder the problem together. I stared at the mass of identical red wires for a while, then, I don't know exactly why, reached out and touched one wire. I suppose something deep in my brain saw something undefinable was wrong.
Anyway, I just touched the wire and it promptly fell out of its connector. He had forgotten to crimp it.
There's a large gap between theory and the real world.
As to the original question, glad you got it diagnosed! But yeah, breakers, GFCIs, receptacles, switches, fixtures, and wire fail or get damaged all the time. I don't think there were any "good old days" where electrical stuff was higher quality; it's always been mostly ****** cheap stuff.
You can get more reliable switches and receptacles for a bit more money (and wire is pretty much wire), but 99% of the breakers, boxes, fixtures, etc. builders use has always been the absolute cheapest trash available. GFCIs are proliferating, and quite a few are complete junk.