I don't buy it. That's clearly the sun until it reaches that red line and then it shrinks and disappears. I've never seen anything like that happen in the sky. Moon or sun. It's super weird.
It's kind of a fun synchronicity though as just after seeing that video, I watched episode 2 of 3 Body Problem where the same sort of thing happens!
That's the moon, and it looks like it's increasing cloud cover + dawn causing camera to decrease overall exposure.