Looked online, and it was suggested there might be condensation in the head.
My cook 24 hour cook was already into the 5th hour. What to do?
I then double bagged the meat, added hot water to a large dutch oven, put my meat in the pot, put a thermometer in the water to monitor the temp, put the lid on. It is like the smokers "crutch", to prevent the stall.
It takes quite a while to come up to temp, but it should save your cook.