Yeah. I found using the Drag and Drop behaviour works poorly when your trying to use it with setPosition() when limiting area.
I have a thought on how you can do this
Don't Drag and Drop your slider icon.
Create an invisible drag and drop object over your up/down slider sprite.
set Y position of your slider to the Y of your Drag Box.
This will limit your slider sprite to the Y axis.
You will also need to check for Y minimum and maximum ranges. You can do this with a heavy inline if statement or 2 extra sub events.
slider.y = ( (drag.y < min) || (drag.y > max) ? (drag.y < min ? min : max) : drag.y )
don't forget to reset your drag box on drop :)
here is a tutorial. Overkill for you needs but you never know what helpful information you can find.
Now if there is a way to limit an particular objects axis. That would be cool, but I have no idea if that exists. Still a noob here :D