Diagnosis
Something is physically obstructing the lifting columns, or the internal gear/spindle is binding. Grinding is bad; stop using it.
How to Fix It
First, power off and unplug the desk. Inspect the entire length of both metal lifting columns. Look for any obvious debris like a cable, cord, or piece of packaging stuck in the mechanism. Carefully remove anything you find. Manually raise and lower the tabletop a few inches by hand to feel for grit or hard spots.
If That Didn't Work
If the noise is coming from inside the column and you've ruled out external blockages, one of the motorized legs is likely failing. You'll need to contact Fully support. They'll diagnose which leg and can send a replacement column assembly.
Heads Up
Never spray lubricant like WD-40 into the columns. It attracts dust and can ruin the internal mechanism. If debris was the cause, a dry, clean cloth to wipe the exposed column is all you should use.