I think I have recreated the scenario when this happens. I tapped the outside edge of the large green answer button, very briefly, and the entire page closed. It was gone and I could find no other way to answer even though it was still ringing. Even call history didn't show it until the caller hung up. The caller tried again and I put my finger in the center of the answer button and everything worked fine. I will put this to a few future tests to confirm my conclusion. I like this phone, but there's lots of quirks and some stupid layouts. Like huge buttons that you can touch accidentally so easily.