I am getting flashes whenever I wake the display, it gives a flash(burst) at the top of the screen, and also realised that the always on display is turned on but it doesn't show. (My phone is updated to newest)
As a starting point please try > Clear Cache Files from the phone's System Partition Section > https://www.samsung.com/uk/support/mobile-devices/how-do-i-clear-the-cache-on-my-device/ You may need to insert your earphones or hook upto a powered On Laptop to access the Clear Partition Section. This may help with lag or stutters as this clears the phone of old/unused or broken cache files.There is also a Repair Apps option in the Menu System too.
