I supplied an example on zkfiddle again.
http://zkfiddle.org/sample/b9isjp/4-ROD-Listbox-with-draggable-set

In a listbox with alot of items, there is the following problem:

1. Select the first item
2. Use the scrollbar to scroll to the bottom of the list
3. Select the last item
4. Now Shift-Select an item some lines above the bottom item

Now the selection looks like the screenshot i provided.

This only happens if i set draggable to any value on the listitem.