Our Whirlpool Microwave came installed in our new manufactured home. There was no problem for the first 14 months. The beginning of the 15th month the microwave began to give off sparks in the back left corner of the interior cooking area about every 20-25 times it was used. I never witnessed this, it was reported to me by the kids. A couple of weeks into the 15th month the microwave had a meltdown in the interior (the cooking area). The cover of the area that vents (looks like louvers in the upper portion of the interior) had melted and was giving off ash of a papery black consistency as...