Hot take: spent 3 hours chasing a bad ground that turned out to be a 15 cent fuse
Last Tuesday I had a Civic in the bay with headlights flickering and I swore it was the relay, so I swapped it and of course nothing changed. Turned out the fuse in slot 12 had a hairline crack you could only see when I wiggled it, and a fresh fuse fixed the whole thing in 30 seconds. What's the dumbest little thing that made you feel silly after you finally found it?