Hello,

I seem to be stuck on a problem when dragging one item from one list to another list it generates a duplicate item on the list it got moved to.

Here's a pen: http://codepen.io/anon/pen/HrCoG
The set up for this pen is having one list of items with an id and with a column property.
I then have two ng-repeats that make use of that list of items but one is filtered by "column:'a'" and the other one is filtered by "column:'b'".
When dragging an item, on beforeStop updates the item's column property so that it gets listed on the correct list.

How you can mimic this:

1. Pick up "10 Gmail (b)"
2. Drop it anywhere on the left list
3. You should see:
   * "10 Gmail (b)" has been added to the bottom of the left list
   * "03 Gmail (a)" has been duplicated

I think it clones the item in the left list with the same index of the item that was moved in the right list.

This doesn't seem to happen when moving an item from the left list to the right list.