Temperature incorrect

I did a Brisket for Xmas, I tried using the Ironwood L but I was not hitting my temp targets for the cook at a certain time. Ended up using the 885 to get the cook times back on track.
Have to say, it was cold outside. So I went to my Pit Boss. My Timberline XL did come with some kind of bluetooth probes. Now I can understand why. Still, I have not used them. Just goes against the grain somehow.