RadTreeView and RadTreeViewItem ExpandAll() method sets the IsExpanded property to True to all items even if an Item has no children to display. This causes an issue when using the DefaultImageSrc and ExpandedImageSrc properties as the last-level items will be displayed with an ExpandedImageSrc as their IsExpanded property it set to True. However, as these items have no children, they should use the DefaultImageSrc.