That's not what is happening here. It uses gravity to generate energy as the mass going downhill is significantly greater than the mass going back up. The mass of the load is used for "powering" the regenerative braking system (resistance is converted to electricity, stored in the batteries) when going downhill. The batteries are now charged when at the bottom. The heavy load is removed from the train. The generated power is used to take the train with significantly less mass back up to be refilled. There is no "perpetual" energy here. Basically the fuel is the load. It still takes energy to load and unload the payload. No magic here. It's just a function of how much mass can the train take downhill, how much regeneration occurs during that operation, and how much energy it takes to take the empty train back up to the top.

Just as you can take a tiny regenerative toy car, give it a few little revving pushes on the floor (let's say 4 feet of regeneration), you can let it go and have it go 100 feet, as all that mass you used from your arm to charge the battery was transferred (obviously not 100%) to the battery. It's not perpetual motion. It's just converting mass into energy. Pure physics here.

This is the same concept when using water, rocks, sand etc. and gravity for batteries. It's just a simple transfer of potential energy.

I mean it is clickbait but it is also a thing that can easily work and there are already mining trucks that do this.

They work because they transport matter from a higher place to a lower place and therefore are much heavier downhill then uphill.

It’s not perpetual motion, it’s just moving things downhill with extra steps.

The extra steps are useful for sure. Storing the generated energy in batteries works on a route where the net cargo movement is downhill even if there are some uphill sections along the way.

A normal truck uses it's brakes constantly when going down hill, turning all that potential energy of the cargo into heat. This truck charges batteries to slow itself down via a generator. At the bottom, it weighs much less, thus even accounting for loses, there's enough energy to get the "lightweight" truck back to the top.

Of course it's not really a perpetual machine. It only works as long as there is enough material to transport downhill.

They're gaining energy by taking bits of the hill down the hill.