I purchased a used car from an individual, it had some hacky alarm system spliced in under the dash which malfunctioned quite comically at the grocery store (if it weren’t for the fear of being stranded with a car full of frozen foods) after we had owned the car about a month. That one was such a mess, I managed to identify its components and clip it out, leaving the factory harness undisturbed - would have been a bit more challenging if the system had actually cut some wires that later needed to be re-spliced.