I've been experiencing a problem with the proximity sensor (face/cheek detector) when making or receiving phone calls on beta 6. Shortly after I put the phone to my face, the call attempts to switch to a Facetime call - presumably because the proximity sensor didn't correctly disable the display, and part of my face has touched the button to trigger that behavior. This is happening on an iPhone 4S. Never had this happen before, but I've had it happen at least three times since installing the latest beta. Anybody else experiencing this?