Diagnosis
That's called "drift" or "settling," and it's usually the control box's anti-collision safety feature kicking in. It thinks it hit an obstruction.
How to Fix It
The most common fix is to reset the desk's lower limit. Unplug the desk. Manually lower the tabletop all the way until the columns are fully closed. Plug it back in. Now, using the handset, press the down button. It might not move, which is fine. Then press 'up'. This recalibrates the starting point and often clears the false obstruction signal.
If That Didn't Work
There might be a minor voltage issue or a glitch in the control box. Perform a full power reset: unplug the desk from the wall for 5 full minutes. This lets any residual charge drain. Plug it back in and test.
Heads Up
If the desk is actually hitting something physical (a cable caught underneath, a drawer hitting the frame), it will do this every time. Do a visual sweep to make sure the path is completely clear, including underneath and behind the legs.