MouseDraggableBehavior mousedown pass through

I've got a bunch of sprites that use MouseDraggableBehavior. If they're overlapping, and you click on the top one, every single sprite in the 'stack' gets the click, and you end up dragging all of them. When you 'mouseUp' the top sprite gets the message and stays but the rest of them end up stuck to the mouse pointer.

What I want is for a click to only hit the top sprite. I'm assuming I'm missing a simple flag or option somewhere, but can anyone provide assistance?