The SconnieQ method is foolproof! Ok, I'm biased. I think either your probe or probe placement was causing the issue. The meat itself just does not cook that way. So, I would probably adjust the placement of the probe. But... I also have multiple probes, so the more you can put in there the better. There are so many fat pockets and odd spaces in brisket, that multiple probes helps with peace of mind. Go by the lowest temperature that registers on the probes.