Unless the sensor is faulty. But highly unlikely as a diagnostic test would indicate that. Even with my big head if I'm holding the phone to my ear, I can be close enough without it touching my head and the screen is deactivated. I can still see the bottom half of phone because to is so long.
Now ear buds or or using the speakers to talk are not always possible. But if the recording option is on the screen, close the settings before the call.
I don't have that feature yet, so I don't know where the activation icon is. I mentioned an easy way to test the proximity sensor without going through the diagnostic. Dial voicemail, then hold your hand over the front camera. See how close your hand has to be for the proximity sensor to activate and stay activated. Most people, consciously or unconsciously tend to move the speaker away from their head. At the same time that they do that, they move the lower end of the phone toward their face because they are either angling the phone or think the mic needs to be close to their mouth. Let's face it, holding a square flat object to your ear is uncomfortable and in most cases the volume level for calls is loud enough that there can be some distance between one's ear and the device and still have clarity.
