Как сделать Popup подвижным в C# WPF более одного раза?

Я создал пользовательский элемент управления, который использует

        <UserControl .......           
         MouseMove = "UserControl_MouseMove" 
         MouseLeftButtonUp = "UserControl_MouseLeftButtonUp">

Мой раздел PopUp кода:

<Popup Name = "CustomTablePopup" Placement = "Center" IsOpen = "False" PopupAnimation = "Slide" MouseLeftButtonDown = "CustomTablePopup_MouseLeftButtonDown" AllowsTransparency = "True">
        <Border x:Name = "roundBorder" BorderThickness = "0" CornerRadius = "10" Background = "Yellow">
          <Border.Effect>
            <DropShadowEffect Color = "Black" Direction = "-360" ShadowDepth = "40" Opacity = "0.7" />
          </Border.Effect>
          
          <Grid Width = "Auto" Height = "Auto" Background = "White">
            <Grid.RowDefinitions>
                <RowDefinition Height = "40"/>
                <RowDefinition Height = "*"/>
            </Grid.RowDefinitions>

            <!-- PopUp Header -->
            <!-- Style for the Border Colour -->
            <Rectangle Grid.Row = "0" Fill = "Gold" Opacity = "0.8"/>
            <Grid x:Name = "GridHeader" Grid.Row = "0">
                <Grid.ColumnDefinitions>
                    <ColumnDefinition Width = "250"/>
                    <ColumnDefinition Width = "*"/>
                    <ColumnDefinition Width = "Auto"/>
                    <ColumnDefinition Width = "200"/>
                </Grid.ColumnDefinitions>

                <!-- PopUp Window Buttons -->
                <Border Grid.Column = "3" HorizontalAlignment = "Right">
                    <Grid Background = "Gold" Opacity = "0.8">
                        <Grid.ColumnDefinitions>
                            <ColumnDefinition Width = "Auto"/>
                            <ColumnDefinition Width = "Auto"/>
                            <ColumnDefinition Width = "Auto"/>
                        </Grid.ColumnDefinitions>

                        <Button Style = "{DynamicResource HeaderButtonStyle}" Grid.Column = "2" Background = "Transparent" BorderBrush = "Transparent" Click = "CloseButton_Click">
                            <StackPanel Orientation = "Horizontal">
                                <Image RenderOptions.BitmapScalingMode = "HighQuality" Source = "/Resources/close-window-image.png"/>
                            </StackPanel>
                        </Button>
                    </Grid>
                </Border>
            </Grid>

            <Grid Grid.Row = "1">
                <Grid.RowDefinitions>
                    <RowDefinition Height = "*"/>
                    <RowDefinition Height = "*"/>
                </Grid.RowDefinitions>

                <Label Grid.Row = "1" Content = "This is the Custom Table Popup"/>
            </Grid>
            
            </Grid>
        </Border>
</Popup>

и я создал одноэлементный класс, который обновляется только после изменения параметра:

public class PopUpMovement
{
    private PopUpMovement() { }

    private static PopUpMovement _instance;
    private static readonly object _instanceLock = new object();

    public static PopUpMovement Instance()
    {
        if (_instance == null)
        {
            lock (_instanceLock)
            {
                if (_instance == null)
                {
                    _instance = new PopUpMovement();
                }
            }
        }

        return _instance;
    }

    public bool draggingPopup { get; set; }
    public bool CustomTablePopupClicked { get; set; }
}

Мой код в коде usercontrol:

    private Point startPoint;
    private double initialHorizontalOffset;
    private double initialVerticalOffset;
    private Point initialMousePosition;
    private Point startDragPoint;
    //private bool CustomTablePopupClicked;

    public UserControlPage()
    {
        InitializeComponent();
        CustomTablePopup.MouseMove += UserControl_MouseMove;
        CustomTablePopup.MouseLeftButtonDown += CustomTablePopup_MouseLeftButtonDown;
        CustomTablePopup.MouseLeftButtonUp += UserControl_MouseLeftButtonUp;
    } 

    private void CloseButton_Click(object sender, RoutedEventArgs e)
    {
        if (CustomTablePopup.IsOpen == true)
        {
            CustomTablePopup.IsOpen = false;
        }
    }

    private void UserControl_MouseMove(object sender, MouseEventArgs e)
    {

        if (PopUpMovement.Instance().draggingPopup)
        {
            else if (PopUpMovement.Instance().CustomTablePopupClicked)
            {
                Point currentMousePosition = e.GetPosition(this); // Get the mouse position relative to the UserControl
                double offsetX = currentMousePosition.X - initialMousePosition.X;
                double offsetY = currentMousePosition.Y - initialMousePosition.Y;

                CustomTablePopup.HorizontalOffset += offsetX;
                CustomTablePopup.VerticalOffset += offsetY;

                initialMousePosition = currentMousePosition; // Update initial position
            }
        }
    }

    private void UserControl_MouseLeftButtonUp(object sender, MouseButtonEventArgs e)
    {
        if (PopUpMovement.Instance().draggingPopup == true)
        {
            PopUpMovement.Instance().draggingPopup = false;
            PopUpMovement.Instance().CustomTablePopupClicked = false;
            Mouse.Capture(null);
        }
    }


    private void CustomTablePopup_MouseLeftButtonDown(object sender, MouseButtonEventArgs e)
    {
        // Store the mouse position
        //draggingPopup = true;
        //PopUpMovement popUpMovement = PopUpMovement.Instance();
        //popUpMovement.draggingPopup = true;
        PopUpMovement.Instance().draggingPopup = true;
        initialMousePosition = e.GetPosition(this); // Get the mouse position relative to the Window
        Mouse.Capture(this); // Capture mouse at the UserControl level
    }

Это работает нормально, если пользователь перемещает всплывающее окно в первый раз, однако, если пользователь хочет переместить его снова, ничего не происходит, оно остается фиксированным. Итак, как я могу исправить код, чтобы пользователь мог перемещать всплывающее окно куда угодно?