Something sure isn't right. The MES max temp is 275 and there is no way a 15 pound bird can cook to 160 in three hours at that temp. I'd expect at least double that time.
First, check how hot your MES is getting.
Second, try an instant read thermometer (if you have one) to double check your probe.
Third, re-insert the probe somewhere else. If you hit a bone or if you have it inserted too far or too shallow, it will read incorrectly. The point of the probe should be as near to the center of the breast as you can get it.
Finally, do the old-fashioned test by wiggling the legs and wings. They should be really loose and the meat should be pulling away from the bone a little bit. Your bird has a beautiful color, but the drumsticks don't appear to have shrunk much.