I have had the bass for over 8 years. I replaced the original pick-ups with Demarzio's when I first received the bass. It just started doing this. The E and A strings sound fine when plucked but the D and G strings break up or don't sound at all. I tested it on a couple of amps as well as changed cables with the same result. I have no idea where or how to begin to troubleshoot this issue. I hope someone can give me feedback.