Ed's right - if the autotune completes its cycle, it should turn itself off. That's the way the older generation worked, too. Matt - might be worth setting up the autotune again, just to be sure.
Ran autotune again yesterday, same thing. When I power cycled the unit it started flashing AT again. Had to go in and turn it off again. ??? I smoked a bacon wrapped venison backstrap afterwards at 225deg and saw the temp swing as high as 234deg. After that one swing, it held pretty tight to 225. Probe is hard mounted per your instructions and auto tuned using 3 bricks as a heat sink. Other than having to turn auto tune off, it seems to be operating ok.