Adjust dot-correction values for LEDs to compensate for the dimmer perceived
brightness of the outer LEDs that need to swipe a larger area.
(Mostly) fix the frequent glitches in the picture stability.

Seems the hall sensor was getting stray signals from the motor coils or the
cable supplying current to the motor.

Attempt to filter that out by ignoring periods that seem to be too far off
what we expect.

I still saw a couple of glitches shortly after start, so might need some
fine-tuning, but it seems to help a lot, at least.