My tonearm wiring insulation became worn, made a slight intermittent hum, wiggled the wire, found it, being re-wired now.
you can use any common wire for a separate ground wire, thus you can substitute any interconnect cable you know does not hum to prove your phono cable is not the problem (or is, unlikely). you can use the phono cable for an interconnect (omit the ground attachments, another way of proving it’s not the cable.
cartridge wires: while on, simply touch end of joint of the wire on the pin (making a good connection) with a small plastic handled screwdriver. one at a time. hum changes? goes away? then remove with needle nose pliers, tighten, re-install. Or, just remove/tighten/reattach, never hurts to be sure.
keep in mind: whenever you move a cable or any piece of equipment, the other end? adjacent cables both ends?