It doesn't shut off. To balance it needs to accelerate or decelerate to keep its position under the rider. If the rider goes fast enough there is not enough power margin to accelerate and so it can no longer provide the balancing function. There are haptic clues that the margin is being approached. The proposal is to add more clues.
The following video explains the problem and the reason it is a bad recall, in particular because there is a far more dangerous issue, but also because there already is feedback.
