Product review (2 stars): Zip ties - temporary fix for when the wheel prongs break
Certainly this component could be better designed to last longer.  Photo below illustrates a temporary fix when the prongs holding the wheels on fail.  In short, use a zip tie (the black stripe) cut short and with the head to the inside.  The wheel won't slide and so pulling the rack in and out won't feel as smooth, but the wheel won't fall off either which can cause the rack to fall. Credit where it's due - I got the idea from a service technician.

Good luck.