Wii U Gamepad Volume Slider Stiff

Hello everybody, I'm having a slight problem with my Gamepad at the moment. Since yesterday, my gamepad's volume slider has been smooth and very responsive when sliding it on and off. Then today, when I tried to slide it down, it stiffened up and became difficult to move. At first I thought maybe some visible debris had gotten trapped in their somewhere and I went around it with a q-tip. No change still stiff. So I tried to get even further in with a small, sharp knife. No change. Has anybody had this problem before and knows a way to fix it? I'd appreciate the feedback. Thanks!