sounds like they're giving you the shaft. And not the one for the crank. 3 motors? 2 didn't work and the 3rd used! As Bronze stated, take it back and chalk it as a lesson learned. Find a different retailer.
Here's a good tutorial on how to set up and fine tune those motors. It's from forum member AI.Fisherman: https://docs.google.com/document/d/1...QUZq2qXXE/edit