Are you saying that with the coax disconnected at both ends there is a short between the center conductor and the putter shield? If so the first I would try is to remove the coax connectors and check the raw cable. Usually shorts are due to a connector failure. Only other way is that a nail or screw penetrated the cable along the path.
'17 Redwood 36RL and '19 GMC Sierra 3500 DRW for retirement "snow-birding" and travel! Me, wife and 2 small dogs.