I had the same problem and it's really simple to solve! The 16 dots you're seeing is the light from the LED backlight. In front of the backlight there's a plastic cylinder very casually glued over it (thanks LG) that diffuses the light, when that drops you see the LED light directly projected onto the screen which causes the white spots. You just have to dismantle it (not too hard), buy some glue and paste those plastic pieces back.