The callbacks isLeaf(), getChildCount(), getChild() are called after opening some nodes for non opened TreeItems.

Example (s attachment):
1. Open 'Sophis e' --> callbacks are ok
2. Open Bond (child of 'Sophis e') --> callbacks for parent 'Sophis e' (maybe an error), callbacks for parent 'Bond' (ok), callbacks for parent 'Calypso' and its subtrees (is an error), callbacks for all other parents (is an error)

The problem gets attention when the tree renders large data amounts.