Impossible to answer calls from lockscreen

[OperaGhost]

Since a few days, when my phone rings the screen turns on, but remains black, with only the top row icons. The phone app doesn't seem to open, if not when the caller ends the call.

Sometimes the first call after I reboot the phone works, but then it's back to black screen.

The only way I have found to answer a phonecall is to drag down the top drawer menu, choose the gear icon for opening the options, enter the pin (or fingerprint) and unlock the phone, swipe down to open the top drawer again, then click on the incoming call notification to open the phone app.

I checked the permissions of the phone app (which I didn't touch in the first place), but they all seem fine. I even tried resetting all apps preferences, but with no result.

Model is G8441

Android 8.0.0

FW 47.1.A.12.179

Can anyone help?

Thanks

Claudio

[NunoSEN2]

Hi @OperaGhost;

Did you tried test the device in safe mode to discard any third party app acting? (Safe mode) 

[OperaGhost]

Hi Nuno,

thanks for the kind reply.

Unfortunately it does the same even after I did a reset of the phone and installed only a very few third party apps. Safe mode makes no difference too.

On the icons toolbar on top there is no telephone receiver too, qhen the phone is ringing, unless I follow the steps I mentioned above to unlock the screen

Edit:

The build after pperforming the restore from Xperia Companion is now 47.1.A.12.205

[NunoSEN2]

@OperaGhost;

If after performing a software repair with Xperia Companion tested the device without installing any backup or third-party apps the problem remains there is nothing more to do software side, maybe is better your device hardware be looked at by your local Sony Support Team.

There is another thing you can try that is replacing the SIM card by a new one. 

[OperaGhost]

I tried the reset again, by first deleting the backup I had on gdrive and not installing any app.

I also chose not to install any security lock from the inizialization procedure.

The phone worked properly until I enablled the security (fingerprint + pin), then the same behaviour started. If I disable the security again, the behaviour remains not right, though in that case I get the phone receiver icon in the top bar, which would at least allow me to answer, but the phone app doesn't automatically open full screen as it should.

If that helps, when enabling security, I chose not to have notifications on the lockscreen (the setting I always had on my phone). Needles to say, chenging the notification settings for the lockscreen didn't bring back the correct behavour of the phone app.

[Misha7887]

I know exactly what you're talking about. It seems like due to the slow screen brightness adjustment, the caller is not visible outside or under bright light. Making it almost impossible to answer the phone. When I am indoors, I don't seem to have the issue. Is this what you're reffrefer to? 

[OperaGhost · Accepted solution]

Actually in my case the telephone app was not on the screen at all.

I found the cause and it had nothing to do with the software at all. There was a very small stain on my display, that unfortunately was right over the proximity sensor. That made the sensor always think that the device was being held close to the face, and so it disabled the phoneapp and turned the display black.

I got suspicious when once the app opened when the telephone rang, but then I wasn't able to close the call because the app wouldn't show again after I moved the telephone away from my ear.

Thanks to everybody who has given his/her contribution, and sorry for wasting your time on such a trivial issue, but I can assure you it wasn't trivial at all until I was able to discover the cause (my phone was close to useless for its main function - receiving calls!).