Can you feel any play in it at all? If you can it might be either the lock washer, the steel bit holding it together on the inside, was pressed on too tight. Or, it could be that the holes for the pin were drilled a bit too deep. Or since it's a brass part it may have oxidized a bit somehow on the inside. If you look around the set screw, can you see a bit of green and/or white gunk? Another possibility may be that some little shaving from the manufacturing process has jammed something up inside. Even if you can't see or feel anything definitely wrong you could first try giving your button a soak in the suggested jewelry cleaner to see if that will help loosen anything in there up. Of course if all else fails send electronicstix a message they probably know better if there's a way to get your button working or will do something to fix or replace it.