Hi tomdw,
Just to clarify part of your problem, are you saying that at the time you took the brisket out of the cabinet the heating element was not producing any heat? Did you get any error codes? Also are you using a third party temperature probe, if so what type?
I don't have a digital, but I haven't read anything about others having the same problem as you are. I would start by cleaning the temperature sensor off, and checking the sensor contacts to make sure they are clean and free of debris.
Other problem areas could be you may have some type of short in the sensor cord, so that may need to be replaced, or the sensor itself may need to be replaced.