All logical stuff there but there's also the reflections, glare and lens flare coupled with people taking pics/video through glass and also not being "still" when doing so.

I remember some years back some cops claiming they were being followed by a "UFO" and when they slowed down, so did it, when they speeded up, the "UFO" did too and when they stopped, it stopped too. What they actually saw was reflected light from their own cop-car!!!!