Screen turns black during phone calls on BQ E4.5

[Andreas Friede]

Since OTA10, the screen goes black immediately after initiating an outgoing call on BQ Aquaris E4.5.

This should only happen when phone is held up to the ear. (Which is triggered by the sensor). But it happens also when I hold it in my hand. I take care not to cover the sensor.

This is annoying because when a user wants to use the UI of the app (i.e speaker-on/off), he has to hit the powerbutton first to activate the screen.