I gave two different sites with different themes, and the problem is the same. The thing is in the WP Lyte plugin. It much helped with mobile version but desktop one suffers a lot.
It is clear what is happennig. A videoframe doesn’t hold the place for itself and shifts the content down after having been loaded. The question is why it behaves like this.
If we take a post without any video, then we notice a place for a picture.