Basically, wooden and stone buttons have the same exact inventory name ("Button") and should be corrected to have the prefix for the type of button it is ("Wooden Button" and "Stone Button", respectively). Basically, do the same thing you did with the pressure plates. I'm not sure if this is either intended or an actual bug. Please thank you for reading this, and I expect it to be fixed in either the next 1.8.1 pre-release, 1.8.2 or the 1.9 snapshots.