Diagnosis
The desk's internal height calibration has drifted. It uses a motor rotation count to estimate position, and over hundreds of cycles, that count can get slightly off, causing it to think it's higher than it is.
How to Fix It
Re-teach the desk its true range. Hold the 'M' button and the UP arrow for 5 seconds until it beeps. The desk will slowly rise to its maximum. When it stops and beeps again, immediately press and hold the DOWN arrow. It will descend to its minimum. This full-cycle reset re-maps the height sensor.
If That Didn't Work
The memory itself might be corrupt. Clear all saved positions: press and hold 'M' and the number '1' for 10 seconds until all LEDs flash. Then reprogram your heights.
Heads Up
After the reset, you must re-program your memory positions. They will be wiped.