I second the opinion , get vinegar in a cup , get it heated for a minute in the microwave now dip only the metal part in the hot hot vinegar keep the cup with a plastic ,keep it that way for an hour,take it out and cleanse it with a coarse cloth. Use WD40 after the oxidation is gone. I had the same issue with my one of my Chord Crimson Plus unfortunately , wrote a mail to Chord UK ( David excellent communucation) and ProFx ,they replaced my cable with a brand new one. I'm a Chord customer forever , speaker cables to interconnects to anything cable.