Volume button only increases or decreases until it reaches the extent of range. I'm assuming there is something in the settings that controls this. I turned on "control with buttons"
Volume button on iPad Air is one directional. It will either increase in volume or decrease and go to mute. It will then stay and not reverse direction. I assume it is something in the settings that I have not set correctly. I have the "control with buttons" on.
iPad Air Wi-Fi, iOS 7.0.1