I assumed frost was from condensation of moist air due to leaky gaskets. After replacing the ice chute gasket and getting no improvement, I later noted two large cracks in the ice tray that were probably letting moisture into the ice maker. The cracks were not easy to see until I emptied the ice tray and flexed the tray. Big gaps opened up at the cracks. When full of ice, the tray flexed and opened the cracks, letting in the moist air. I replaced the ice tray assembly and it seems to have worked.