In my research thus far, the AMOLED screen technology is to blame. When the display circuits get old or damaged, they don't sustain current at low power settings. In LED screens, a back light controls brightness, but AMOLED screens send current to each pixel for brightness control. If the circuit is damaged, or any corrosion has built up inside, this could attenuate the current below the point required to sustain light flow. I see this problem with some LED and CFL lights on motion sensor switches. Just enough current goes through the motion sensor to keep it's circuits active, and that current causes a flicker in the light. With the screen though, since the problem is only resolved when you increase the brightness just a bit above minimum, it seems anything that lowers the display power (auto brightness for example) will cause it to flicker if this setting gets too low. I also noticed that before the screen locks on timer, it dims to low power for a few seconds and flickers as a result. There are apps...