Top drawer - Take it out & check for anything obstructing it. Check the wiring harness. It will have a linkage attached to it to pull it out of the way when you close the drawer. The early ones were plastic & will break. The later ones & the replacement ones are steel. Also check the retainer clips situated at the back end of the slide rails, make sure they are facing the incoming drawer. Sometimes they flip over toward the back.
Lincoln Appliance NZ, December 2009