TouchScreen not responsive in specific part on Xperia Z

[KentTai]

Hi people, I used the phone normally and all in a sudden the screen has random clicks. But after one day, the random clicks are gone, but the part above the on screen buttons is extremely unresponsive, the rest of the screen is working fine. This is annoying when I try to tap the keyboard out, I'll need to rotate the phone and tap then rotate it back. Is this hardware or software issue? I tried repairing the software, hard restart, factory reset, nothing helps. 

Anyone faced the same problem? Is the problem solved? Help please~

Thanks a lot.

[Uliwooly]

Take your phone to a Sony repair center

Also, test your phone with 

https://play.google.com/store/apps/details?id=com.sonymobile.androidapp.functiontester

[KentTai]

Tried the app, that's the part that it doesn't recognize any touch.

[Uliwooly]

Take your phone to a Sony repair center as it appears to be a hardware issue

http://www.sonymobile.com/global-en/support/contact-us/