I have never seen plastic rise in temp once the micro powers down. That would be new to me.
I Had a forum member in the shop just this morning, and we took a 1 1/4 cup of plastic, Initial time of 2:30, then another 30 before we ever stirred it. I then took it to 400 plus, and reheated it to 400 plus and we shot some clear baits.
Hes a essential guy as well. I was just showing off.

What most people don't realize is that heat stabilizer also separates, and you can not mix a box, that has no air pocket in it effectively.