Flashing screen

[Hades123123]

Occasionally my son's screen flashes once dark once bright after locking the problem ceases but every now and again it appears Sony xperia xz premium

Co jakiś czas ekran mojej sonki miga raz ciemny raz jasny po zablokowaniu problem ustaje ale co jakiś czas znowu się pojawia Sony xperia xz premium 

[Uliwooly]

@Hades123123

I've edited your post as this is an English only forum, you can use Google Translate to reply and/or post. 

Does it happen all the time or just with specific apps?

[Hades123123]

Cały czas nawet na startowym ekranie 

All the time, even on the start screen

GT