Probably an RV shop, since it involves cabling inside an RV. Are we talking about wiring between a dish and the receiver, or the receiver and the tvs? The usual technique is to temporarily run a new wire around the suspected one and see if that fixes the problem. If it does, then figure out how to replace the defective one.
Regular satellite techs don't know much about RV and mobile satellite, nor do they want to spend the time to learn and/or figure out what is awry. Blaming problems on stuff you can't see is an easy out.