DIAGNOSIS: Some side-to-side flex is normal at full height, especially with a wide desktop, but excessive wobble usually means the frame isn't tightened properly or the floor is uneven.
FIX: Grab your hex key set. 1) Check the bolts connecting the two legs to the crossbar underneath. There are usually four on each side—tighten them firmly. 2) Check the bolts that attach the feet to the legs. 3) Most importantly, check the bolts securing the desktop to the frame. They should be snug. Overtightening can strip the particleboard, so stop when you feel solid resistance.
IF THAT DIDN'T WORK: The floor might be the issue. Put a level on the desk surface. If it's not level, the frame is twisting. Use the adjustable feet on the bottom of each leg. Turn them clockwise to extend and compensate for a dip in the floor until the desk is level. This removes twist and reduces wobble.
HEADS UP: A dual-motor Vari will be more stable than a single-motor. If you have a very long desktop (over 60 inches) and heavy monitors on arms, expect some monitor shake at standing height—that's physics, not a desk defect. Consider a monitor mount attached to the desktop, not the wall.