Drag and Drop on Tree column

[NearEarthObject]

Hi,

still in need of re positioning parent child object through Drag and drop function, I switch from nested grid to tree.
I use flat format who was more logical for me but I try both with same trouble :
https://jsfiddle.net/NearEarthObject/o879bfwg/

One time again, child are moving without any trouble the one to the other.
But when I try reorganizing parent row, I got a console error : Cannot read property 'children' of undefined.

What is amazing, I took inspiration of https://paramquery.com/pro/demos/dnd_tree example.
In this case that works fine.

Any idea how I could solve my issue ?

Thanks in advance

[paramvir]

In its current setup, drag & drop in treegrid works for non root nodes only. Is it possible for you to add a common root node at the top?