If I remember correctly, the problem I had with servos, the threaded internal end of spline (where servo arm would normally attach) is hollow and allowed leaking oil to enter servo case and short circuit the dial pot or micro electronic board. Some electrical contact cleaner probably could save it. But I replaced anyway. Suggestion is if servos are hollow shaft and no screw is inserted into shaft then put a spot of silicone to plug the hole. Should not have oil present to even leak into there but that is another story
