Hackers Help: How to prevent shelf sag in large Pax wardrobes?

IKEA pax wardrobe prevent shelf sag
Photo: IKEA.com

I’m looking for suggestions for preventing shelf sag in Pax wardrobes.  Some, even not heavily loaded, shelves are sagging and causing the side panels of the wardrobe cabinet to spread pulling out the small plastic pins that hold the shelves in place and eventually allowing the shelf to drop.  What remedies have you used to prevent this from happening?

~ David