Diagnosis
The glide assemblies for the Top Rack (sometimes called the Silverware Basket) are damaged or disengaged. The plastic tabs that lock the rack to the glide rails have broken.
How to Fix It
You need to replace the top rack glide kit. Part number is WD49X20094. Remove the entire top rack by lifting it up and out. Unhook the old glides from the tub rails. Snap the new left and right glide assemblies onto the rack. Carefully align and lower the rack onto the tub rails until it clicks into place.
If That Didn't Work
Inspect the metal rails on the tub itself. If they are bent or damaged, the rack will not seat properly. The tub rails are not separately serviced; the entire tub must be replaced if damaged.
Heads Up
Do not overload the top rack. It is designed for utensils and lightweight items only. Heavy items like large spoons or tools can strain and break the glide mechanisms.