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Can you check if the same occurs in safe mode?
http://talk.sonymobile.com/t5/FAQ/How-to-boot-your-phone-into-safe-mode/m-p/348008
Test your device with this app
https://play.google.com/store/apps/details?id=com.sonymobile.androidapp.functiontester&hl=en
or dial
*#*#7378423#*#*
Even if you do not cover it?
That might be something network related.