Egg set up for low slow cook - temp stable at 250 for a couple of hours - top vent basically closed - bottom vent open about 1/4 inch - then after several hours - temp spiked to over 650 - the egg needs new gaskets - could that have been enough to intro enough air flow for that temp build up - I can not think of anything else - may that poor Pork Butt rest in peace....
