After this video, I saw it two more times. One in 2018 and the other 10 days ago.

I saw it pretty close in 2018. Its color was just like mercury. So is its shape. Just as mercury ripples and rolls, so did this one. It did not have a fixed shape. It floated in the air, about 100 meters from me. It was 2-3 meters in diameter. Then it stopped. It remained stationary in the air. In the meantime, its shape was changing like mercury again. The route it followed in the air was extremely smooth and slow-moving.
It waited for about 1 minute. Then it began to rise at an angle of 90 degrees. So it started to go up. At this time, it began to glow very strongly. It could no longer be shaped. It was like a strong source of light. It was like a light bulb. It rose in the air and disappeared.

It seemed to me that it could not be man-made. I have never seen such a flying object before.
The only possibility is that it could be a remote-controlled vehicle developed for espionage purposes. Or an alien spacecraft. 😄🛸