Xperia Z2 :: In-call Button Press - Notification Panel Open With Different Options Activated / Deactivated

I had this problem previously and was waiting for Lollipop thinking it will get solved, but it looks like I might have a faulty proximity sensor. When I'm in a call, sometimes I hear the sound of pressing a button, and when I take the phone away from my ear to check what happened, I keep finding the Notification Panel open with different options activated / deactivated. Sometimes I find it directly in Settings, in Battery Usage, in Date/Time, I think it depends on which option is pressed in the Notification Panel.