Proximity Sensor Problem

[K.I.R.K]

it seems my proximity sensor is not working. when i receive a call the display stays black. is there any solution or does anybody knows a dialer that has the option to deactivate the sensor?
(currently i'm using crDroid 6.3, but it happened in other rom's too)

 

[K.I.R.K]

found a solution that works for me: it's an app called "Proximity Screen Off Lite"
this app uses the device administrator permission.

+++update+++
worked for a certain time but stopped because of unknown reasons