It's best to open a support ticket on this at :http://www.tekgear.com/contact/
Check to make sure the mechanism isn't gummed up. Pockets can get quite "linty" and it can gum up the mechanism.
To do this, make sure you have some crazy glue on hand, and remove the cap. It's glued on so you have to do a bit of gentle twisting and pulling. Once off, you should be able to see the joystick. Make sure it is free of debris. It may need a shot of compressed air or an alcohol swab to clean it out.
Once cleaned and working again, put a super small dab of crazy glue on the joystick stalk and slide the cap back on. Remember with crazy glue a little is a lot. You don't want to goop it on, you want a super thin layer to get the best bond.