I got one of these free from a Freecycle ad. Having read about the same problem all over the web, and watched many repair videos, I fixed mine with minimal effort: Take a rubber grip pen and pull off the rubber sleeve. Cut off a small piece from the end, approx. 1/6 to 1/8". (You can always trim it down later). Then slice one side and keep slicing off miniscule pieces until you can fit it as a circle into that spindle hole of the motor end where the teeth wore off. (Mine showed six worn spots which I assume were once teeth or bumps to hold the blender stick and attachments snugly). Then I used Loctite to glue into place. My Smart Stick now works beautifully with all its attachments. (The grip pen came from Dollar Tree and Loctite from Home Depot.)
Kit Kelley
October 2016