How do you explain its behavior?
Looking at the demo video, this machine looks fake to me. The person who assembled and exhibited it in the video used some trick to move the machine. I believe there is a platform that can tilt and contains a background attached to it, a table on top of it, a demonstrator standing on the platform and a camera (And lighting) kept on this platform. This possible setup is shown in below drawing. (Apologies for poor drawing skills)
This gives an illusion as if the black wheel is somehow transferring the energy to one of the large wheels and then storing it back from inertia. But looking at the demo carefully, it is evident that a lot of energy is wasted (while stopping and some from friction). Interestingly wheels are very smooth to minimize friction, but off course, it can not be zero.
How to debunk this “Perpetual Motion Machine?”
It is not possible (in current state ;) of our universe) to reverse the entropy or in other words create free energy device.
Such tricky videos attract many views and generate good revenue for the channel.
In my opinion, the device motion itself is not faked , but there may be camera trickery involved to hide an accomplice, acting as an additional energy source.
Look at 0:49 seconds - he gives the blue wheel a spin - he is putting energy into the device. It is certainly believable that the inertia stored here would be sufficient to propel the device to the left.
Every time the device is stopped at the LHS of the screen, the blue wheel momentarily goes out of frame - perhaps for an assistant to add to the spin - the shadows visible certainly suggest an extra pair of hands to me...
As noted by @alephzero, the device rolls to the right naturally at 0:22, suggesting that the table is slightly tilted in that direction. The manufacture needs only to hold the blue wheel slightly above the RH wheel without letting them touch, to allow it to roll to the right with gravity.
- Moving Left - energy supplied by human spinning the blue wheel
- Moving Right - rolling downhill
- Additional energy input provided when the blue wheel is out of frame.