Diagnosis
The telescoping inner column on one leg is binding. Debris or a lack of lubrication on the chrome inner tube is the most common cause.
How to Fix It
Lower the desk to its lowest height. Wipe the entire length of the inner chrome tube on the noisy leg with a dry cloth. Apply a thin coat of white lithium grease or dry silicone lubricant to the tube. Cycle the desk up and down a few times to distribute it.
If That Didn't Work
The plastic guide bushing inside the outer column may be cracked or worn. This requires disassembly of the leg column to inspect. Contact Seville Classics support for a leg replacement if the noise persists after lubrication.
Heads Up
Do not use WD-40 or oil-based lubricants. They attract dust and will make the problem worse within weeks.