I think it's just space junk.  None of the pieces I saw made any drastic direction changes once seen, and the light/dark was just shiny bit in the sun or not as something turned.  Tons of stuff up there under 6" long that would look bigger in a shot like that if nearby.

Look for speed/direction changes is the quickest way to filter out stuff that is likely not interesting, doesn't guarantee it but erases a whole bunch of prosaic explanations that would be thrown out anyway to write it off.  Sudden large acceleration or hard turns  suddenly make the interesting ones even more so once you see how many thing adjust go in straight paths.