Diagnosis
The control box is not properly synced to both motors. The legs are out of sync from the initial setup.
How to Fix It
Lower the desk to its absolute bottom position. Unplug the desk. Disconnect the motor cables from the control box. Plug the desk back in. Reconnect both motor cables securely. Press and hold the down button for 10 seconds to initiate a full reset and synchronization.
If That Didn't Work
A motor cable might be faulty. Swap the left and right motor cable connections at the control box. If the problem switches legs, you need a new cable. If the same leg lags, the motor itself is likely defective.
Heads Up
Never operate the desk for more than a second when the legs are out of sync. It will twist the frame and cause permanent damage.