Hi i have a xperia z1 and i had the screen changed more than once due to breakages and now after the latest screen change the screen flickers randomly or when calls come through. I also noticed this usually happens when there is no strong network.
I suggest that you try to repair the phone software using PC Companion..
Before repairing your device you may want to backup your information first. Check out this topic for more information on how to. How to backup?
If the issue should still remain I think that this needs to be examined and fixed at a repair center. For more information about how to submit your phone for repair and where, contact your local support team.
