The grate feet ware out and/or they fall out and get discarded. The repair is easy but finding / ordering the part can be challenging.
AppliancePartsPros.com made it very easy. I put the GE part number in their search area and the part popped up. Added them to my cart and purchased them. They arrived in two days and I save 20% over the official GE Parts site. I will use AppliancePartsPros again.