TreeListBox generates phantom items when selecting via code

If I select a TreeListBox item via its IsSelected property before I expand the RootItem phantom items are created in the TreeListBox. Here's a simple example which shows the issue. To reproduce launch the app and hit the button before expanding anything in the TreeListBox - that will select an item in the tree. If you then expand the items on the left a few phantom entries will be displayed

Screen Shot Here

<Window x:Class="ActiProTest.MainWindow"
        xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
        xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
        xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
        xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
        xmlns:local="clr-namespace:ActiProTest"
        xmlns:ac="http://schemas.actiprosoftware.com/winfx/xaml/grids"
        mc:Ignorable="d"
        Title="MainWindow" Height="450" Width="800">
  <DockPanel LastChildFill="True">
    <ac:TreeListBox       
      SelectionMode="Extended"
      MultiSelectionKind="SameDepth"
      IsRootItemVisible="True"
      Width="200"
      DockPanel.Dock="Left" 
      x:Name="_tree">
      <ac:TreeListBox.ItemAdapter>
        <local:LayerAdapter/>
      </ac:TreeListBox.ItemAdapter>
      <ac:TreeListBox.ItemTemplate>
        <DataTemplate>
          <TextBlock Text="{Binding Name}" />
        </DataTemplate>
      </ac:TreeListBox.ItemTemplate>
    </ac:TreeListBox>
    <Button Click="Button_Click">hit me</Button>
  </DockPanel>
</Window>

using ActiproSoftware.Windows.Controls.Grids;
using System.Collections;
using System.Collections.ObjectModel;
using System.ComponentModel;
using System.Windows;

namespace ActiProTest
{
  /// <summary>
  /// Interaction logic for MainWindow.xaml
  /// </summary>
  public partial class MainWindow : Window
  {
    MyItem ItemToSelect;
    public MainWindow()
    {
      InitializeComponent();
      MyItem root = new MyItem() { Name = "The Root" };
      for( int ix = 0; ix < 5; ix++)
      {
        var subItem = new MyItem() { Name = $"child {ix + 1}" };
        for(int iy = 0; iy < 5; iy++)
        {
          var subsub = new MyItem() { Name = $"sub {ix + 1} {iy + 1}" };
          if (ix == 2 && iy == 3) ItemToSelect = subsub;
          subItem.Children.Add(subsub);
        }
        root.Children.Add(subItem);
      }
      _tree.RootItem = root;
    }

    private void Button_Click(object sender, RoutedEventArgs e)
    {
      ItemToSelect.IsSelected = true;
    }
  }


  public class MyItem : INotifyPropertyChanged
  {
    public event PropertyChangedEventHandler PropertyChanged;

    bool _IsSelected;
    public bool IsSelected
    {
      get { return _IsSelected; }
      set
      {
        if ( value != _IsSelected)
        {
          _IsSelected = value;
          PropertyChanged?.Invoke(this, new PropertyChangedEventArgs("IsSelected"));
        }
      }
    }

    ObservableCollection<MyItem> _Children = new ObservableCollection<MyItem>();
    public ObservableCollection<MyItem> Children
    {
      get { return _Children; }
    }

    public string Name { get; set; }
  }

  public class LayerAdapter : TreeListBoxItemAdapter
  {

    public LayerAdapter()
    {
      IsSelectedPath = "IsSelected";
    }

    public override IEnumerable GetChildren(TreeListBox ownerControl, object item)
    {
      return (item as MyItem).Children;
    }

    public override bool GetIsSelected(TreeListBox ownerControl, object item)
    {
      return (item as MyItem).IsSelected;
    }

    public override void SetIsSelected(TreeListBox ownerControl, object item, bool value)
    {
      (item as MyItem).IsSelected = value;
    }

    public override bool CanHaveChildren(TreeListBox ownerControl, object item)
    {
      return (item as MyItem).Children.Count > 0;
    }
  }
}