The tablet's screen suddenly turns off when I change position.

[Gilad]

I have a one year old tablet Xperia Z WIFI with Android version 4.4.4 and I have a strange problem.
When I use my tablet and I change its position, the screen suddenly turns off, and even the power button does not turn it on.
Only when I change the position of the tablet again, the screen turns on and goes to the lock screen.

This problem occurs several times a day - but not always.
The problem started about a month ago and also occurred in version 4.4.2.
I tried to reset the device includes deleting a memory card, but it did not solve the problem.
Anyone know the problem?

[Alexander1]

Hi and welcome to the community! Since you're new please be sure that you have checked out our Discussion guidelines.

I would suggest that you try to boot your phone into safe mode to see if the problem may be related to any 3rd party app that you have installed in your phone:

http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008#U348008

If the behavior still persists in safe mode I would suggest that you try to repair the device software using PC Companion: 

http://www.sonymobile.com/update

In PC Companion, press start on Support Zone > Start on Update the phone/tablet software > click on the blue highlight (Repair my phone/tablet). Do this without the phone connected. Follow the instructions on screen to perform the repair.

[Gilad]

Thanks for your answer.

I found the root cause of this issue.
It's the cover case!
LabatoFlip Smart Stand Case Cover.

I bought this case a year ago and i liked it very much.
after it got broken I bought a new one, and somehow it causes this weird phenomenon.

I need to look for new cover case now