items property on NSToolbar returning empty collection for macOS15

We have a xib file that contains a toolbar with some items in it. The toolbar has an IBOutlet defined in its files owner. Before macOS 15 - we were able to reach the items in the toolbar by using the items property.

The File Owner for the xib containing the toolbar is a NSViewController

e.g.

@IBOutlet var theToolbar: NSToolbar!
 required init?(coder: NSCoder) {
        super.init(coder: coder)
        Bundle.main.loadNibNamed("ToolbarDesign", owner: self, topLevelObjects:nil)
    }

and then later in code...

func getItems()
{
       let items:[NSToolbarItem]? =  mainRightToolbar?.items
}

Prior to macOS15 - items would contain the NSToolbarItems specified in the xib design. Now, in macOS 15 - the items array is not nil but doesn't contain any items either.

What needs to be don't for macOS15 specifically to enable the items property of NSToolbar to work again?