Comments by HugeHugh (Top 1 by date)

Thanks for your reply, John.

I modified my Window_Loaded code as follows, but the bug is still persisting:

private void Window_Loaded(object sender, RoutedEventArgs e)
        {
            TabItem tiNew = new TabItem()
            {
                Header = "Outer Tab 1",
                Content = new DummyClass()
                {
                    DummyMember = 1
                }
            };

            OuterTabs.Items.Add(tiNew);
            
            TabItem tiNew2 = new TabItem()
            {
                Header = "Outer Tab 2",
                Content = new DummyClass()
                {
                    DummyMember = 2
                }
            };

            OuterTabs.Items.Add(tiNew2);
        }

I am using a new and different variable for the 2nd tab, tiNew2, which has no relationship to the 1st tiNew. It still has the same problem.