Its like how a $40 toaster and a $400 one both make toast until you load them up with four slices at once, the cheap one just gives up. Same thing with switches, the box only falls apart when you actually push it.

Whoa, forty years with zero moss?! That's wild!

Honestly half the battle is just having someone who hasn't been staring at the same truck for three hours. Mike probably saved you way more than the $40 in parts, that fresh set of eyes thing is real. I've lost whole afternoons to stuff that would've been obvious if I'd just stepped back for five minutes.