DO you let the temp. get to 160 before you take them out? Don’t they get to dry. Because they still keep cooking after you take them out don’t they.
With sticks and other sausages, you should be cooling them rapidly when they reach 160. That way they don’t keep cooking and it sets the ingredients in the casing.
You can cool them the fastest in a tub of cold water. Because sticks are so small, they can be cooled fairly quickly in a refrigerator or outside if air temperatures are cold. The faster they cool, typically the less they wrinkle.