I just got a Yamaha YCL-221 II. The lower tenon has only the rubber rings and no cork. I understand that this by design but it leaves the joint a little loose compared with the middle joint. It rocks a little when playing and gets out of alignment far too easily. Any ideas? The rubber on the rings looks fine. I don't get it but at this point, I wish it had some cork! Anyone else with this experience? Any way to fix it? Defect in just mine??