It's the display on the radio or whatnot refreshing. LED brakelights and your computer monitor do the same thing. You just can't see it with your eye (it looks like it's constantly on), but a camera picks it up.
Since when liquid crystal-based devices do refresh ? We're talking LCD monitors here, right ? Not sure about the brake leds ( they may be using sinewave power signal to prolongate led life ), but afaik no such thing for LCD monitors.
And what in the name of god do brakelights and (any) monitors have in common at all ?
edit:
it just came into my mind that i've seen OLED displays which do flash, but because of power economy as well.
it could be they use oled in the stereo frontend.
