I had a similar experience, Justin, losing LR & RF lights at first &/or second switch settings. Condition set in after body/paint work at rear. Feed from left light assy. to license plate lights is not polarity-protected by connector configuration.....and got reversed. A little crazy-making for a bit, though I didn't lose a diode. Given your familiarity with electronics -- and my lack of it -- I thought when I read "diode" I'd just keep to myself, but I think Al's got it.
Hi Al; got my H2O sensor rejuvenated OK in Albuquerque. And salutations, Dick; I hope I'm able to get out to see your project on the road this season. Denny