Hi earvedson,
There are two likely possibilities. Either the servo is not configured correctly, or your servo is bad and needs to be replaced.
First, double check that the servo is plugged into the EBB correctly. Next, remove the servo from the pen arm, and see if it still behaves this way, even if you change the pen up and pen down position. It’s important to check this because if the servo arm is in the wrong place (from the setup stage) it can behave exactly as you have described, running all the way to one end and then get stuck there.
If the servo is still not working, then it will need to be replaced. Please use the contact form at our shop to request a replacement: http://shop.evilmadscientist.com/contact
