Once I had a dodgy input on an oldstyle stick, it turned out one of the pins in the hood had worked itself loose somehow. I opened the hood and you could clearly see it out of position. Pushed it back into place and that fixed my problem. That might be worth a look.
You could use a multimeter to determine if it's your switch. I rarely see switches completely die, usually when they go bad they will still complete a circuit but they become unreliable (only working when pressed a certain amount, for example).