The issue occurs when unlocking the device by fingerprint scanner or face unlock. Does not matter. The display simply starts blinking during the process of user recognition and then basically two options. The device is unlocked and I am getting to the main screen or it is unclear if the device unlocked or not, but it is the black screen. The issue occurred a few week ago, I first thought it happens due to the cold climate in my country, but the the display now blinks no matter where you are, in the warm premise or outside. I am very careful with the smartphone, never dropped it or accidentally hit, or spit anything on it. Please advise what can be a solution? Should I pass the device to a service or it can be an impact of cold or recent update?