I have seen this issue being raised many times on this thread,
That many times when a Prius hits a pothole or a bump and you are breaking at the same time the car behaves very abruptly and releases the brake temporarily
That is not fault in fact that is the ABS unit kicking in and it is fulfilling its role which is that it is supposed to release the brake pressure on any tire which comes to a complete halt to prevent the car from spinning out of control
Because if any single tire comes to a complete halt meaning the tires speed is 0 and the car is still in motion that will result in a serious accident
Though the feeling is quite strange but the right thing to do is not release the brake in such a moment that would result in a very risky situation
@bilalalam can further comment