It’s possible that you are experiencing false trace or the effects of an accelerating fragrance oil. What temperature are your melted fats and lye just before you mix them? In false trace the batter starts to thicken as the hard fats start to solidify. As you might imagine, it‘s recipe-dependent. If the batter is fully emulsified before it goes into false trace, it will still make soap, but the chances of stearic spots will go up. Small batches can be tricky because they tend to cool off quickly, especially if the ambient temperature in the room is cool. With bigger batches the batter will often start to heat up on it’s own and may become more workable. In my experiences, small portions of batter don’t do that. Accelerating FOs can be problematic under the best of conditions.
If you want to share your recipe, working temperature, and details on any FOs used, we can do more troubleshooting for you.