Whats hot? Hot to the touch? Water boils at 212 degrees, can you keep your hand in boiling water for more then a few seconds before you have 3rd degree burns?

185-200 degrees is the "hot zone" for BL motors. They can and will still be just fine if you get one to 200 degrees but most of the time neodymium magnets start to demagnitize at that temp.

Check your temps and gear it accordingly. Start back at a 15T and go up.