Flipping magnet motor
Ask yourself why the rack devices are needed to flip the magnets 180°. Simply because they won't flip by themselves. Something must do work to flip them, and that work comes at the expense of something else. The work required to flip the magnets comes from the rotational kinetic energy of the armature, and that slows it down.
Each flip occurs in opposition to the force due to the field of the stationary magnets, and this exerts retarding force on the moving magnet, slowing the armature's rotation. In fact, this device, started from rest will not complete 1/3 of a revolution before stopping.
This is a common theme in perpetual motion illusions. Villard de Honnecourt's wheel had swinging hammers, which naive examination suggests ought to give the wheel a forward impulse. But actually, while falling, they exert a backward impulse on the wheel, which one can easily discover by building a model and trying it. The same thing happens whenever a mass is moved within or on a rotating wheel. You may gain a bit of speed for a short interval and lose it during another interval, for a net gain of zero. The rules of nature are stacked against perpetual motion inventors so that nature always wins.
The animation misleads in another way, for it shows the armature moving with constant speed. In reality, any combination of discrete magnets will have a motion that speeds and slows cyclically.