My XPE started not letting me lower the ring volume when choosing not to answer a call. Before this, if I happen to have forgotten to put my phone ring on vibrate or silence, and my phone started ringing, I was able to lower the volume all the way to silence by continuously pushing "volume down" button until the phone went silent. Now I'm noticing that while ringing, pushing the volume down button does nothing while ringing and the ring volume is unaffected by pushing the volume down button. Any ideas?