I remember my first butt on the 3D when I got it. Pure panic; so I called Tony (an original forum member) and he essentially said it is done. I was close to the 17 hour mark. The bone pulled clean. Very tasty and moist. So here is what I believe happened. My probe was in meat and the tip in a fat pocket. At some point (maybe during the stall), the fat rendered and the tip was now in a void or lost contact with the muscle. I believe that happened. I use an instant read and probe butts and briskets in a couple of places just to verify. I start probing around the 12 or 14 hour mark.