Oxidation on surface of cable under clear jacket

Wondered if anyone has had this problem.  I have a pair of “Oval” cables I was going to reintroduce into my system.  They’re 15 years old.  I noticed that green oxidation had formed over a length of the cable under the clear jacket.  Since there is shrink tubing over the spade connector, so I can’t tell if the oxidation has reached the connector.  Problem is the manufacturer’s warranty was over many years ago.  They weren’t inexpensive. Seems others have had the same issue.  I guess I’ll give them a call to see what can be done, but I’m not optimistic.  I do have another manufacturer’s cables I can use if this can’t be remedied.. Your thoughts?