Problem:
After updating from 1.7 to 1.8 behavior of event.oldIndex/event.newIndex changed when using draggable property to restrict sortable elements. In 1.7 index values were relative to sortable elements array only, but in 1.8 they are relative to all elements present in sortable parent, not only those ones which are actually sortable (limited with draggable property).
JSBin/JSFiddle demonstrating the problem: