Diagnostics mastery note: logically ruling out a readily testable possibility is only (somewhat) logical when one hasn’t exhausted all other possibilities. Displeasing and successful diagnostic tests that ought not to differentiate but do are how one exposes issues hiding in the blind spots of other experts. (If they hadn’t explicitly said ‘I have no ideas left’ in as many words, I probably wouldn’t have posted at all.) Here is an idea they hadn’t openly said they considered. The reasons this idea might or might not pan out are still interesting to me! TIL! But it was a beautiful and consumer-accessible scalpel of diagnostic and earned me a walkthrough of the signal contamination specifics by the senior truck tech who showed up to help the lesser truck tech, so perhaps it’ll help another.