When drag is finished DRAG_DONE event doesn't come to node from which it was started.
To reproduce:
Run netbeans project from attachment
Drag from nodes with text "Drag me" to text field with text "Drag here"
Each of "Drag me" nodes has onDragDone handler but it doesn't get triggered when drag is over. However you can see that drag was done because text in "Drop here" text field will change to class name of node from which drag was started.