Thanks for your reply 🙂
When you check a node for example parent1 , tree expand and collapse immediately.
I think there is a bug here , i have to expand the node again to see sub items.
Do you have any idea about it?
I tried your example again as a few days before but the provided example does not work.
But I would like to suggest something to try.
Try to add async: false in the settings of the AJAX.
I hope this will help.
The data is loaded on demand and for this reason, it cannot set the items with checked checkboxes.
While the collapsing case immediately after you expand the first item is because you use the collapseItem method (row: 130) for it.