Thanks @dynacohum
I actually did try replacing the rca plugs at the end of the output cable. Same result. It’s not a changer table and so the cable has plugs only at the one end. There’s a junction box of sorts under the deck where the tonearm cable is pinned and the output cable is soldered.
I’m going to try replacing the cartridge with an inexpensive sumiko while also cleaning the contacts along the way as suggested. Fingers crossed.

