At random instances the whole screen "blinks" either white, or black.
It lasts for a fraction of a second and happens 100% randomly while using the phone.
It was apparent on WP8.1 and also on W10m, so it has something to do with the hardware.
As I said above, it is not something huge, but it is annoying when it happens cause it really hearts your brain..
Occurs more often when the brightness is very low. Increase the brightness so you would not see that weird issue.
But it won't help you at night because you will be forced to dim the brightness