When making Summer sausage, I can't seem to get the internal temp up to 155 deg. without raising the temperature above 165. When I do raise the temp higher I get what is called grease out, the meat cooks and shrinks. I start at 140 for 4 hours and raise to 165. It has been in 8 hours with an internal temperature of 125. I checked the temp probe with a digital thermometer and they are both the same. Any help would be appreciated.