This is 100% of a fake. This is easily done with a torch and the reflection on the big window. You clearly can see the light beam meeting the window on the lower left side of the window, moving the same way as the "UFO" does. And did you notice how how they try to avoid to center the "UFO" on this video? Of course, as they try to avoid to make the beam, meeting the window, visible. And the "UFO" itself is not the meeting point of the beam itself, but the reflection of the torch light left behind the camera holder (a matter of viewing angle glass in relation to torch holder and camera holder) inside the room. So we have two subjects on the window's glass: the meeting point of the beam and the (a bit dirty) glass itself as well as the reflection of the torch depending on the viewing angle. A really poor fake, but a nice idea anyway.