777 small wing panel moving all the time during landing
That control surface is called a flaperon.

The flaperon functions as both a flap and an aileron to provide roll control, as with an aileron, and increased lift and drag, as with flaps. The flaperons on either wing move down together as flaps, and move up and down opposite each other as ailerons.

In the video, steady movement following that of the surrounding flaps from one position to another is an indication of operation in the role of a flap. If we could see the other wing we would see that flaperon moving in sequence. However, the short up and down movements, as opposed to the stationary flaps, is an indication of operation in the role of an aileron. If we could see the other wing we would see that flaperon moving opposite the flaperon in the video.