It is quite possible that it's not really a bug or a flaw. These devices use LED lights for illumination, and dim them by switching them on and off very fast. At the lowest brightness settings it is quite common to get these glimpses of flashing, but it feels like you imagined it. That's because your peripheral vision has a higher sensitivity to flickering than the the focused part of your eyesight.
Try looking directly at the screen at the lowest brightness, and then spending a little time looking past the screen, keeping the screen in your peripheral vision.
Most computer LCD monitors that use LED backlighting also have this issue.
There is, of course, the chance that there is a problem with your device, but I think that this may be more likely.