I just checked mine and I would say it moves about the same amount as yours in the video. My is functioning perfectly. I think your mag is most likely OK. How the gun shooting and cycling? That will give you the most definitive answer as to whether your mag is functioning properly.
I think i know what is causing this by the way, the ball bearing where the magazine is spinning on is pretty narrow, way more narrow than the surface of the magazine itself. Shouldn't these sizes be the same?