Now I’m sure there are others on here who are far more knowledgable than me on these matters, but isn’t popping when you touch the strings due to a lack of earthing rather than just shielding? It does sound like the seller hasn’t done any basic checks before sending out and the QC at Musicman is very suspect. How very disappointing for you, if you keep it I think you’ll always be looking for faults and never satisfied with it. If it can really be solved by shielding and your competent to do it, get in touch with the store and ask for a massive partial refund to make up for their incompetence and your inconvenience. There is something in law requiring goods to be of “ merchantable “ quality and this bass sounds like it wasn’t. If the shop won’t cooperate threaten them with Trading Standards.