I have checked thermometers - when I first found this I thought mine was busted so I checked with another and got the same result.
The briskets I get are generally longer, wider, and shorter/thinner than a standard brisket. They are also a lot leaner - byproduct of the diet and being free range. I'm going to do a clod this weekend to see what kind of results I get from that.
I've been really happy with the grass fed steak and roast cuts and I love the flavor I'm getting but I just want the brisket to be more tender