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.