If you Google "replacement navigation joystick chrysler" you'll see that there are a few companies who will replace/repair your joystick issue. I've never dealt with any of them but it may be a cheaper alternative to buying a new radio. Good luck.
2008 XK Limited 5.7L. 93,500 miles. 3.5"/2" Heavy Metal Leveling Lift. Spider Trax Spacers. Bilsteins. JK rims w/ 255/75 /17.