I've never made any sausage and have to ask, what's "fat out'
It's a term used in the sausage field when the fat in the sausage renders down and melts and turns into a liquid form.... Usually happens when your cooking temps are to high...
I'm going to calibrate (boiling water) my PID controller and probe, But i'm pretty confident that's in order as it was reading correct ambeint temp... I even backed my max temp down to 170 from 175 for the second batch...
