Weird behaviour droping in nested nestedSortable list

[astromediaonly]

Sorry if its somehow my mistake but this happening and i cant figure out why:
If i try to drag item from sublist to bottom it allows me to make it child of parent list but not in reverse and not if i drag from sublist to top. I would like to disable moving between levels at all (for specific rules idealy).

Here is JsFiddle example. (Im not sure how to include this library to it so i have copied whoole code - my specific code is on bottom.

If I drop item A.A.C to the left it should not make it on same level as item A.A or am i mistaken?

PS: Sorry for my english, its not my primary language.