It is sun.
Again, so are you saying the sun magically jumps in front of the mountain?
Here it is before sunrise:

And then as the sun comes out:


It takes away a large chunk of the mountain.
So again, are you saying the sun magically jumps in front of the mountain or magically passes through it? How does it manage to do that?
What about later on in the video, we have the sun here:

Then as the cloud passes in front, the sun magically shrinks:

Why is it magically shrinking here? It doesn't move drastically, and then just after the cloud passes it goes back to its normal size. It is quite easy to notice in the video.
And don't worry, it happens more than once, like here:


So what is causing this magical size changing?
The sane explanation is glare, but you are saying that is the real size of the sun, not glare. So what causes the sun to change size? Why isn't it observed to just flash smaller at any other point when there is nothing between the viewer and the sun?