If the problem was battery related then I would think that the scooter would roll to a stop and not stop abruptly. I am not familiar with the Genesis Hornet scooter though so I may be wrong about that.
I am taking a guess here that maybe the brake on the handlebar, which is an electronic brake, is malfunctioning and intermittently telling the controller to apply the brake when the brake lever is not being pushed. Or the problem could be that the handlebar brake wire is damaged and its wires are short-circuiting with each other momentarily. A malfunctioning controller could also cause that type of problem.
If you are able to get it apart and look at the wires between the brake paddle and controller and between the battery and controller that would be a good place to start from. Hopefully, the problem is something simple like a loose connector can be pushed back in to fix it.
Genesis went out of business this year (2018) and even when they were in business the only parts they sold were batteries and chargers, so finding parts for it is likely to be difficult.
We can most likely supply battery chargers and tires/tubes for it if a support ticket requesting for these parts is submitted to us.