Vue.Draggable: Nested dragging may cause unexpected DOM change

Our app has two-level nested draggable items and has list defined/mapped.

When dragging an item in the inner list, sometimes the DOM may update incorrectly, and when it happens, the item being dragged will jump to the beginning of the list. The vue data, however, is correct/as expected. So it seems like the DOM is updated inconsistently w.r.t. the event, whereas the vue data is fine.

We tried to make a reproducible demo: https://jsfiddle.net/6sha4vv6/1/

Dragging Wildcard Courses x to the place of Multiple Courses x and release can cause the former to jump to the first position.