What you are experiencing is a limit on attenuation from the yeast you selected. In BS3, there was a change to cap the attenuation based upon the max alcohol tolerance of the yeast as published by the yeast manufacturer. You can bypass this by editing the yeast in the recipe and changing the max tolerance number. Doing this will not change physical reality, however, and your results will highly depend upon fermentation temperature, quality and quantity of viable cells pitched, and fermentation time.