Div with overflow-y: scroll, jquery ui droppable and sortable

Div with overflow-y: scroll, jquery ui droppable and sortable

For several hours scratching their heads on the same problem: http://jsfiddle.net/6kLvLjqr/29/

If drag "sortable 2" "droppable 2", everything works fine. But if you drag the "sortable 12" to "droppable 2", using only the scroll wheel mouse , there are problems. After scrolling you need to move the cursor outside div.cont and only if the element "droppable 2" will take "sortable 12".