Display goes black during a call

When I receive a call and I put the phone close to my head the screen goes black as expected. But then the screen doesn't recover and stays black. I must press the on/off button several time to make it recover. I don't use any screen protector or glass, the screen close to the proximity sensor is clean and unscratched. By using the .12345+= code in the calculator and entering in the test mode I can see that both proximity sensor test and light sensor test fail. The proximity sensor always detect far object untill I put something very close to it. Then, even if I remove the object the sensor remains locked to 0.0 cm. The light sensor always detects 0.0.
This started after a major update of many zen ui apps.
Is there any way to calibrate again the sensors?
Please don't tell me it is an hardware issue, this would be the last of several in the last year.

Hi andrea977,

Please update to 12.16.5.126 and try again,

If problem persists, i would suggest you to go to local service center for a check:

http://www.asus.com/support/Service-Center-All-Countries/

sorry for any inconvenience

Thanks for the suggestion. Updated but still not working. I will just change the mobile with a NOT asus new one. 

I have the same problem too. Firmware update to 12.16.5.126.

hard reset the phone. wipe everything in recovery, it should go away.

Update, if during the black screen I put the sensor under a very intense light (close to the bulb of my desktop lamp) it recovers! Why? Asus? Is there anybody out there? 

andrea977 posted on 2016/10/11 21:30
Update, if during the black screen I put the sensor under a very intense light (close to the bulb of ...

Ciao Andrea... confermo che il sensore funziona sotto forte illuminazione... tu hai provato a fare il reset?

Hi All,

Please try to do a simple hardware test,
go asus calculator app > type ".12345+=" enter SMMI Test"
>single test > Proximity test

have a try.
Thanks.

Emilee_ASUS posted on 2016/10/14 11:25
Hi All,

Please try to do a simple hardware test,

Hi Emilee... the proximity sensor test work only under a very intense light.

klikkoklikko posted on 2016/10/12 14:00
Ciao Andrea... confermo che il sensore funziona sotto forte illuminazione... tu hai provato a fare ...

Ciao, non ancora provato. Vorrei cercare di evitare. Tu l'hai fatto?