I've been using an old Logitech Dual Action(the one without rumble!) since the days of FFXI, it's literally flown around the world twice, been used in hundreds of hours of gaming, and it still works fine
That being said, I don't usually eat while I use it, so I think raseol might be right, it's just dirty. Try rotating the stick around a lot, cleaning what you can get to, and maybe even compressed air.