I built JeepingJohnny's Circular Sock Machine and noticed that the Yarn Stand Brake did not work as I had seen other CSM brakes working in various videos on youtube. I made some slight modifications and now it pinches the yarn. This inhibits the heel spring from stripping more yarn off the cone, thus losing tension.
This .stl prints without supports. See JeepingJohnny's project page instructions for further details.
The author remixed this model.
Added annotations to photo to make the function of this revision more clear.