When one of our bands leads goes wrong, I typically find that the problem is with the plug: either zero or poor quality strain relief for the cable, which permits constant flexing of the wires, so that in the end the wires break through fatigue. Often strain relief consists soley of relatively soft metal 'jaws' being crimped onto the cable. The soldering itself very rarely fails (though it will in the long run if the cable is repeatedly exposed to big temperature changes). I repair all cables these days using Neutrik plugs. Each plug comes with plastic inserts which effectively 'lock' the cable into the plug, and to which the outer shell casing screws. I don't even need to file the metal of the plug contacts to get a good solder joint anymore! Get some of these and look forward to not touching that lead again ...