Do the buttons on the base still work, independent of the joystick position?
Do the LEDs still light up even when the buttons stop working?
If both answers are "yes", it's probably a worn PWM signal cable between the joystick and the baseplate. I'd suggest replacing it with some slightly tougher wire. I've made a guide a while back [https://imgur.com/gallery/XSJVW|on imgur, I'm afraid.] But it should point you in the right direction. It assumes you know how to solder, though.