One thing I can tell you is that my maverick probe consistently reads 5-7 degrees above my thermopen. I just use it as an indicator but I would take a second look at that brisket and make a game plan based upon where I think it actually is at right now. If in fact it is overcooked cool it and reheat it later in juices. if undercooked get it back on while it is still hot and finish it off. I have mistakenly placed a probe in a fat pocket as suggested may have happened and it drove me nuts trying to figure out what was going on. When I sliced it the reason was obvious to me.
2 Primo XL's, 3 (not very) Ugly Drums, 1Ugly Drum, 2 22.5 wsm's, and 2 18.5 wsm's.