Nor-Lake Freezer Norlake Refrigeration 6' x 6' Kold Locker Walk-In Freezer - 6' 7'' High w/Floor "plunger ice makers" Questions

I have a pretty new Amana refrigerator that gets frost build up in the opening of the ice maker. Do you know what is causing that? THE FLAPER IS NOT GOING SHUT REPLACE THE PLUNGER