Phone autolocked on calling apps and not return to normal(main screen)

[AC Question]

I have Sony Xperia Z upgraded to version 5.1.1, the problem is the phone gets autolocked on calling & calling apps such as whatsapp, viber and mobilevoip and the screen is still locked until the other person don't cut it this happens with the whatsapp and normal dialing but with the mobilevoip it doesn't work even the other person do cut the call I can't go to the main screen even with the power button and can't even switch off the phone, unfortunately I have to take sim from the working phone which could damage phone but no choice.

 

[hallux]

I had a hard time following your post, but it almost sounds like "screen pinning" was used. If you tap the app switcher "key" (the square icon) and then enter your PIN or unlock method, you should return to normal operation.