What is the mysterious object flying by in this SpaceX video?

In the last second of this video tweeted by spaceX, you can see an object fly by on screen. Did this come from the SpaceX ship, or is it foreign space junk? If it turns out to be the latter, is that a common occurrence? It seems to me like that could’ve been a very close call with catastrophe.

update: The video is also in YouTube (below) after about T+ 01:01:46 which is about 01:20:07 in the video's counter)

[