"Shift" button not working on mpc 2000xl

Hey guys, if you have a mpc 2000xl, then you know how important the 'shift' button is to the system, it's really difficult to maneuver around the mpc without it. So, I was just wondering if anyone here knows how I can fix the problem, if I need to clean it, replace it, or what?

probably you need to replace it
the buttons are 10$ on mpcstuff.com
or .08$ a piece at mouser if you buy a hundred like i did and replaced all the buttons
and killed my pad sensor or some shit, im never gonna get my 2000xl working