All is true! Well you could resolve it just using careful procedures described in all the threads which relate to this here, but the common areas are to clean wherever there is tarnish from RCA plugs to the cartridge clips, wire crimps, headshell (cartridge carrier contacts), PCB on the tonearm head. The tarnish can get everywhere and even inside the microscopic clips where they are crimped. There is a way to chemically clean them (then re-crimp even tighter) but the absolute best is to pry open the clips with the smallest jewelers screwdrivers possible, clean the surfaces and the wires, and re-clamp. (If you do it chemically and it fails, you'll probably ruin the tiny clip trying to get it to release the tiny wires for proper cleaning). This is a real pain, but it does increase signal strength and reliability. Any nicks on those few soft copper wires inside each sheath and they'll fall off, so be sure they are strong before reassembling. If you solder them, don't allow the solder to run into the clamp portion of the clip or you'll have a mess. They don't really have to be soldered though if it's done well, it's probably the best result.
Muting switch keeps the system quiet during cycling. The cartridge is a form of microphone, similar principles involved. If not muted during cycling you will hear clunks and loud sounds from the table and stylus you'd rather not hear. So those contacts in the right of the pic need to be clean and make good contact in order to have it work well.