I have the same issue. S7 edge Android 8.0. Was working fine until a month ago. Cant tell if its the samsung patch update or not. I have no screen protector, no case. Dialled that number for the diagnostic tool ran the sensor test. No issue with proximity sensor reported. I have cleared my devlik cache, rebooted, enabled and disabled smart stay and it has not fixed anything for me. Would like some help if any