End Cap adjusting
Over time the End Cap might need to be adjusted so that it "hugs" the string adapter more tightly. Hold one end of the cap under hot running water from your faucet for about 20-30 seconds or until the tab shown in the illustration becomes pliable. Gently push that tab inward just a little bit, and then give it a minute to cool. Dry the End Cap and see if it fits better on your String Adapter or if it needs another adjustment.