My thought was that it was a small bug crawling across the aperture lens/filter, not the eyepiece. It follows a noticeable curved path. A satellite would not do that.

A bird or plane might, but a plane would be silhouetted enough to see some detail like wings or the tail. A bird in flight would not have that stop and go jerking motion.

I'm still going with a very small insect on the objective. They look just like that when they land on my glasses.

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An evil person would do the things I think up.