When the electric vehicle is driving at a high speed, it will pause and return to normal, as will replacing the controller and battery.
Did this happen after the controller was changed? Is it normal to pause for a while when starting? If so, it is that the Hall element inside the motor is broken, and then the "universal" controller is replaced to enter the Hall-free state. If it is not the above symptoms, it is that there is a thread inside the handlebar that seems to be connected but not connected.