Diagnosis
User error. The Pulse function on the ONE is not a toggle button; it's a momentary contact button.
How to Fix It
You must press and hold the Pulse button down for the duration of the pulse. Release the button to stop. It is designed for short, controlled bursts. Do not just tap it.
If That Didn't Work
The button itself could be sticking or faulty. If the motor continues to run after you release the button, unplug the unit immediately. This indicates a control board or switch failure.
Heads Up
Continuous holding on Pulse is hard on the motor. Use it for 1-3 second bursts only. For longer blends, use the variable speed dial.