Scroll bug in AvalonEdit

MainWindow.xaml

<Window
    x:Class="AvalonEditScrollBug.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:avalonEdit="clr-namespace:ICSharpCode.AvalonEdit;assembly=ICSharpCode.AvalonEdit"
    Title="MainWindow"
    Width="525"
    Height="350">
    <Grid>
        <Grid.RowDefinitions>
            <RowDefinition Height="Auto" />
            <RowDefinition Height="*" />
        </Grid.RowDefinitions>
        <Menu>
            <MenuItem Click="OnClearText" Header="Clear text" />
            <MenuItem Click="OnAddSingleLineText" Header="Add text (single line)" />
            <MenuItem Click="OnAddMultiLineText" Header="Add text (many lines)" />
        </Menu>
        <avalonEdit:TextEditor
            Name="PART_TextEditor"
            Grid.Row="1"
            HorizontalScrollBarVisibility="Auto"
            VerticalScrollBarVisibility="Auto" />
    </Grid>
</Window>

MainWindow.xaml.cs

namespace AvalonEditScrollBug
{
    using System;
    using System.Windows;

    using ICSharpCode.AvalonEdit.Document;

    /// <summary>
    /// Interaction logic for MainWindow.xaml
    /// </summary>
    public partial class MainWindow
    {
        public MainWindow()
        {
            this.InitializeComponent();

            this.PART_TextEditor.Document.Changing += this.OnDocumentChanging;
            this.PART_TextEditor.Document.Changed += this.OnDocumentChanged;
        }


        private void OnDocumentChanging(object sender, DocumentChangeEventArgs e)
        {
            this.ShouldAutoScroll = this.IsScrolledToEnd && e.Offset == this.PART_TextEditor.Document.TextLength;
        }

        private bool IsScrolledToEnd
        {
            get
            {
                return this.PART_TextEditor.VerticalOffset + this.PART_TextEditor.ViewportHeight >= this.PART_TextEditor.ExtentHeight;
            }
        }

        private bool ShouldAutoScroll { get; set; }

        private void OnDocumentChanged(object sender, DocumentChangeEventArgs e)
        {
            if (this.ShouldAutoScroll)
            {
                this.PART_TextEditor.ScrollToLine(this.PART_TextEditor.LineCount);

                //ApplicationHelper.DoEvents();
                //if (this.IsScrolledToEnd)
                //{
                //    return;
                //}

                //TextEditor.TextArea.TextView.Redraw();
                //ApplicationHelper.DoEvents();

                //if (this.IsScrolledToEnd)
                //{
                //    return;
                //}

                //var vl =
                //    TextEditor.TextArea.TextView.GetOrConstructVisualLine(
                //        this.Document.GetLineByNumber(this.Document.LineCount));

                //TextEditor.TextArea.TextView.Redraw(vl);
                //ApplicationHelper.DoEvents();

                //if (this.IsScrolledToEnd)
                //{
                //    return;
                //}

                //this.TextEditor.ScrollToLine(this.TextEditor.LineCount);
            }
        }

        private void OnAddSingleLineText(object sender, RoutedEventArgs e)
        {
            this.PART_TextEditor.Document.Insert(
                this.PART_TextEditor.Document.TextLength,
                string.Format("{0}--- Line #{1} ---", Environment.NewLine, this.PART_TextEditor.Document.LineCount + 1));
        }

        private void OnAddMultiLineText(object sender, RoutedEventArgs e)
        {
            for (int i = 0; i < 250; i++)
            {
                this.PART_TextEditor.Document.Insert(
                    this.PART_TextEditor.Document.TextLength,
                    string.Format(
                        "----------------------------------------- Very long line #{1} -----------------------------------------{0}",
                        Environment.NewLine,
                        this.PART_TextEditor.Document.LineCount));
            }
        }

        private void OnClearText(object sender, RoutedEventArgs e)
        {
            this.PART_TextEditor.Document.Remove(0, this.PART_TextEditor.Document.TextLength);
        }
    }
}