Hey Steve, can you do like a post mortem check on the cable? Ohm out each line to see what the resistance is on each connector from connector to connector, and check for shorts between the wires too (if there is any continuity (low ohms) between pins on the connector)
I am kind of wondering the failure mode here. Is it wires breaking off the pins/sockets in the connectors. Or how sensitive is the injection if there is still continuity but say 10ohm resistance on the line when it should be less than 1ohm.