Welcome to the forum. Too little info to be of much help. How old is the smoker? Your probes may be bad or it could be the controller. The D models have been upgraded over the years so they have different digital controllers, all manufactured by Auber and have a 1 year warranty while the smoker itself less the controller has a 3 year warranty. On the home page, for the customer, you can see tips for the D models and how to reset the controller to factory specs if you think that will help. On the Auber site, look for the controller (different housing) and you will also find instructions for resetting.
You can also try an auto-tune which might be advisable before doing a reset. If you auto tune, make sure you have a dummy load in the smoker such a a throw away aluminum loaf pan filled with 'damp' sand. Not wet, damp, to simulate meat. It will give off moisture much like a butt or brisket or chicken would. In either case, call up your current PID settings and write them down so you can return to them. A photo or your controller might prove useful to someone who may have experienced a similar problem.