Repro of DynamicData sorting problem

DDSortingRepro.cs

public class ItemViewModel : ReactiveObject
{
    private readonly string name;
    private readonly ObservableAsPropertyHelper<int> sortOrder;

    public ItemViewModel(string name, IObservable<int> sortOrder, IScheduler scheduler)
    {
        this.name = name;
        this.sortOrder = sortOrder
            .ToProperty(this, x => x.SortOrder, scheduler: scheduler);
    }

    public string Name => this.name;

    public int SortOrder => this.sortOrder.Value;
}

public class ItemComparer : IComparer<ItemViewModel>
{
    public static readonly ItemComparer Instance = new ItemComparer();

    private ItemComparer()
    {
    }

    public int Compare(ItemViewModel x, ItemViewModel y) =>
        x.SortOrder.CompareTo(y.SortOrder);
}

public class ItemsViewModel : ReactiveObject
{
    private readonly SourceList<ItemViewModel> items;
    private ReadOnlyObservableCollection<ItemViewModel> sortedItems;

    public ItemsViewModel()
    {
        this.items = new SourceList<ItemViewModel>();
        var sortedItems = items
            .Connect()
            .Sort(ItemComparer.Instance)
            .Bind(out this.sortedItems)
            .Subscribe();
    }

    public ReadOnlyObservableCollection<ItemViewModel> SortedItems => this.sortedItems;

    public void Add(ItemViewModel item) => this.items.Add(item);
}


public class Fixture
{
    [Fact]
    public void foo()
    {
        var scheduler = new TestScheduler();
        var vm1SortOrder = new BehaviorSubject<int>(0);
        var vm2SortOrder = new BehaviorSubject<int>(1);
        var vm3SortOrder = new BehaviorSubject<int>(2);
        var vm1 = new ItemViewModel("First", vm1SortOrder, scheduler);
        var vm2 = new ItemViewModel("Second", vm2SortOrder, scheduler);
        var vm3 = new ItemViewModel("Third", vm3SortOrder, scheduler);

        var sut = new ItemsViewModel();
        sut.Add(vm1);
        sut.Add(vm2);
        sut.Add(vm3);
        scheduler.Start();

        Assert.Equal(3, sut.SortedItems.Count);
        Assert.Equal("First", sut.SortedItems[0].Name);
        Assert.Equal("Second", sut.SortedItems[1].Name);
        Assert.Equal("Third", sut.SortedItems[2].Name);

        vm1SortOrder.OnNext(4);
        Assert.Equal("Second", sut.SortedItems[0].Name);
        Assert.Equal("Third", sut.SortedItems[1].Name);
        Assert.Equal("First", sut.SortedItems[2].Name);
    }
}