I had a lot of issues with wired GC controllers. I actually was getting quite pissed and tired of sending them back to Nintendo. I would ensure everyone had washed hands and no one was playing rough with the controllers. The damn b buttons kept sticking on me. They would get jammed down and barely work as intended. The c stick (yellow stick) would also start messing up (notice right away when playing Melee because that controls the tilt of the character select screen). I sent them a final email saying what ever you do make sure your next controller doesn't suck as bad as this one. That is how the Wiimote + nunchuck were born.
I eventually tried a Wavebird. I never had a problem with b button sticking or c stick going out and still have 4 Wavebirds.