It's not the fabric or batting most of the time. There was probably a hot spot in the microwave. I've noticed lower wattage microwaves have hot spots. You ever put more then one food item on a plate and have one not be as hot as the others? That is uneven heating and will cause hot spots. A 1200 watt will cook a baked potatoe in a couple of minutes. A lower wattage will take up to 12 minutes thus the hot spots get hotter for a longer time.