I have had that happen before. I live in coastal South Texas - lots of heat and humidity! I start drying on racks in air-conditioned room with two oscillating fans constantly running over the cookies until the cookies are packaged. It stopped happening when I stopped drying on a shelf located directly under some high intensity inset canister lights...they produced an inordinate amount of heat right down on the cookies. Has never happened after I started drying on cooling racks under fans! When I'm decorating I also lower the a/c 3-4 degrees lower than we usually keep the house. Hope that helps.