Problems with data binding in TreeView for a custom editor window

[BeginnerPolymath]

When attempting to bind data to TreeView, it doesn’t update the List<TreeViewItemData>() passed through SetRootItems. Additionally, itemsSource returns HierarchyNode instead of the objects of my type nested within TreeViewItemData. I used this manual for implementation (Unity - Manual: UXML element TreeView), but the problems remain the same. It used to work for me before, but now there’s no effect. Moreover, Unity crashes when rebuilding the hierarchy and clicking to expand/collapse a group. The question is, am I doing something wrong? Could I be binding the data incorrectly?