could someone please answer a question for me. i have had a brisket on now for 18 hours at 225 i increased temp to 250.at 9am this morning the internal temp was 161 deg. now 6 hours later it is only 172 deg internal temp. is it common for a brisket to stall this long or take this long to cook?? it weighted 12lbs at start packer. any help is much appreciated. thank you, ryan