Proximity sensor malfunction

[recycledunit]

When someone calls, proximity sensor won't work until you go into the app or tap the small call pop-up in the status bar

[Goodwy]

Does the proximity sensor work in other apps?
Is the sensor turned on or off in the app settings?

[recycledunit]

Sensor is enabled in all settings and works properly in other apps. It seems the problem is only related to incoming calls