WPF animation with custom text on the right cause text to not appear when overlapping entire grid content

Question

I have a user control which contains an animation that I found here by HAdes (I have done some little changes, little color).

User Control:

<UserControl x:Class="My.Apps.WPF.Demo.Controls.UCBusy"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    Height="300" Width="300">

    <UserControl.Resources>
        <Color x:Key="FilledColor" A="255" B="222" R="176" G="196"/>
        <Color x:Key="UnfilledColor" A="0" B="222" R="176" G="196"/>
        <!--<Color x:Key="FilledColor" A="255" B="155" R="155" G="155"/>
        <Color x:Key="UnfilledColor" A="0" B="155" R="155" G="155"/>-->
<!-- Value="#7F000000"-->
        <Style x:Key="BusyAnimationStyle" TargetType="Control">
            <Setter Property="Background" Value="white" />

            <Setter Property="Template">
                <Setter.Value>
                    <ControlTemplate TargetType="Control">
                        <ControlTemplate.Resources>
                            <Storyboard x:Key="Animation0" BeginTime="00:00:00.0" RepeatBehavior="Forever">
                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="ellipse0" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)">
                                    <SplineColorKeyFrame KeyTime="00:00:00.0" Value="{StaticResource FilledColor}"/>
                                    <SplineColorKeyFrame KeyTime="00:00:01.6" Value="{StaticResource UnfilledColor}"/>
                                </ColorAnimationUsingKeyFrames>
                            </Storyboard>

                            <Storyboard x:Key="Animation1" BeginTime="00:00:00.2" RepeatBehavior="Forever">
                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="ellipse1" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)">
                                    <SplineColorKeyFrame KeyTime="00:00:00.0" Value="{StaticResource FilledColor}"/>
                                    <SplineColorKeyFrame KeyTime="00:00:01.6" Value="{StaticResource UnfilledColor}"/>
                                </ColorAnimationUsingKeyFrames>
                            </Storyboard>

                            <Storyboard x:Key="Animation2" BeginTime="00:00:00.4" RepeatBehavior="Forever">
                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="ellipse2" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)">
                                    <SplineColorKeyFrame KeyTime="00:00:00.0" Value="{StaticResource FilledColor}"/>
                                    <SplineColorKeyFrame KeyTime="00:00:01.6" Value="{StaticResource UnfilledColor}"/>
                                </ColorAnimationUsingKeyFrames>
                            </Storyboard>

                            <Storyboard x:Key="Animation3" BeginTime="00:00:00.6" RepeatBehavior="Forever">
                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="ellipse3" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)">
                                    <SplineColorKeyFrame KeyTime="00:00:00.0" Value="{StaticResource FilledColor}"/>
                                    <SplineColorKeyFrame KeyTime="00:00:01.6" Value="{StaticResource UnfilledColor}"/>
                                </ColorAnimationUsingKeyFrames>
                            </Storyboard>

                            <Storyboard x:Key="Animation4" BeginTime="00:00:00.8" RepeatBehavior="Forever">
                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="ellipse4" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)">
                                    <SplineColorKeyFrame KeyTime="00:00:00.0" Value="{StaticResource FilledColor}"/>
                                    <SplineColorKeyFrame KeyTime="00:00:01.6" Value="{StaticResource UnfilledColor}"/>
                                </ColorAnimationUsingKeyFrames>
                            </Storyboard>

                            <Storyboard x:Key="Animation5" BeginTime="00:00:01.0" RepeatBehavior="Forever">
                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="ellipse5" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)">
                                    <SplineColorKeyFrame KeyTime="00:00:00.0" Value="{StaticResource FilledColor}"/>
                                    <SplineColorKeyFrame KeyTime="00:00:01.6" Value="{StaticResource UnfilledColor}"/>
                                </ColorAnimationUsingKeyFrames>
                            </Storyboard>

                            <Storyboard x:Key="Animation6" BeginTime="00:00:01.2" RepeatBehavior="Forever">
                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="ellipse6" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)">
                                    <SplineColorKeyFrame KeyTime="00:00:00.0" Value="{StaticResource FilledColor}"/>
                                    <SplineColorKeyFrame KeyTime="00:00:01.6" Value="{StaticResource UnfilledColor}"/>
                                </ColorAnimationUsingKeyFrames>
                            </Storyboard>

                            <Storyboard x:Key="Animation7" BeginTime="00:00:01.4" RepeatBehavior="Forever">
                                <ColorAnimationUsingKeyFrames Storyboard.TargetName="ellipse7" Storyboard.TargetProperty="(Shape.Fill).(SolidColorBrush.Color)">
                                    <SplineColorKeyFrame KeyTime="00:00:00.0" Value="{StaticResource FilledColor}"/>
                                    <SplineColorKeyFrame KeyTime="00:00:01.6" Value="{StaticResource UnfilledColor}"/>
                                </ColorAnimationUsingKeyFrames>
                            </Storyboard>
                        </ControlTemplate.Resources>

                        <ControlTemplate.Triggers>
                            <Trigger Property="IsVisible" Value="True">
                                <Trigger.EnterActions>
                                    <BeginStoryboard Storyboard="{StaticResource Animation0}" x:Name="Storyboard0" />
                                    <BeginStoryboard Storyboard="{StaticResource Animation1}" x:Name="Storyboard1"/>
                                    <BeginStoryboard Storyboard="{StaticResource Animation2}" x:Name="Storyboard2"/>
                                    <BeginStoryboard Storyboard="{StaticResource Animation3}" x:Name="Storyboard3"/>
                                    <BeginStoryboard Storyboard="{StaticResource Animation4}" x:Name="Storyboard4"/>
                                    <BeginStoryboard Storyboard="{StaticResource Animation5}" x:Name="Storyboard5"/>
                                    <BeginStoryboard Storyboard="{StaticResource Animation6}" x:Name="Storyboard6"/>
                                    <BeginStoryboard Storyboard="{StaticResource Animation7}" x:Name="Storyboard7"/>
                                </Trigger.EnterActions>

                                <Trigger.ExitActions>
                                    <StopStoryboard BeginStoryboardName="Storyboard0"/>
                                    <StopStoryboard BeginStoryboardName="Storyboard1"/>
                                    <StopStoryboard BeginStoryboardName="Storyboard2"/>
                                    <StopStoryboard BeginStoryboardName="Storyboard3"/>
                                    <StopStoryboard BeginStoryboardName="Storyboard4"/>
                                    <StopStoryboard BeginStoryboardName="Storyboard5"/>
                                    <StopStoryboard BeginStoryboardName="Storyboard6"/>
                                    <StopStoryboard BeginStoryboardName="Storyboard7"/>
                                </Trigger.ExitActions>
                            </Trigger>
                        </ControlTemplate.Triggers>

                        <Border BorderBrush="{TemplateBinding BorderBrush}" 
                                BorderThickness="{TemplateBinding BorderThickness}" 
                                Background="{TemplateBinding Background}">

                            <Grid>
                                <Canvas Height="60" Width="60">
                                    <Canvas.Resources>
                                        <Style TargetType="Ellipse">
                                            <Setter Property="Width" Value="15"/>
                                            <Setter Property="Height" Value="15" />
                                            <Setter Property="Fill" Value="#009B9B9B" />
                                        </Style>
                                    </Canvas.Resources>

                                    <Ellipse x:Name="ellipse0" Canvas.Left="1.75" Canvas.Top="21"/>
                                    <Ellipse x:Name="ellipse1" Canvas.Top="7" Canvas.Left="6.5"/>
                                    <Ellipse x:Name="ellipse2" Canvas.Left="20.5" Canvas.Top="0.75"/>
                                    <Ellipse x:Name="ellipse3" Canvas.Left="34.75" Canvas.Top="6.75"/>
                                    <Ellipse x:Name="ellipse4" Canvas.Left="40.5" Canvas.Top="20.75" />
                                    <Ellipse x:Name="ellipse5" Canvas.Left="34.75" Canvas.Top="34.5"/>
                                    <Ellipse x:Name="ellipse6" Canvas.Left="20.75" Canvas.Top="39.75"/>
                                    <Ellipse x:Name="ellipse7" Canvas.Top="34.25" Canvas.Left="7" />
                                    <Ellipse Width="39.5" Height="39.5" Canvas.Left="8.75" Canvas.Top="8" Visibility="Hidden"/>
                                </Canvas>
                                <Label Content="{Binding Path=Text}" HorizontalAlignment="Center" VerticalAlignment="Center"/>
                                <!--<Label Content="Waiting . . ." HorizontalAlignment="Center" VerticalAlignment="Center"/>-->
                            </Grid>
                        </Border>
                    </ControlTemplate>
                </Setter.Value>
            </Setter>
        </Style>
    </UserControl.Resources>

    <StackPanel Orientation="Horizontal" HorizontalAlignment="Center" VerticalAlignment="Center">
        <Control Style="{StaticResource BusyAnimationStyle}">

        </Control>
        <TextBlock Text="Waiting . . ."  VerticalAlignment="Center" FontSize="20" Margin="10" />
    </StackPanel>

</UserControl>

As you can see above in the last lines, I am trying to put a message "Waiting . . ." to the right of the animation so I have used a StackPanel and Orientation set as Horizontal. Ok, no problem until here.

Now I embed this user control into another user control (see below) and I want to overlap the entire content of a grid with the user control UCBusy so I set for it Panel.ZIndex="100". UCBusy appears at the front but only the spinner, the text on the right of the spinner does not appear. Why?

<UserControl x:Class="My.Apps.WPF.Demo.Controls.UCData"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"    
    xmlns:controls="clr-namespace:My.Apps.WPF.Demo.Controls"
    Width="700" Height="250">

 <Grid>

    <Grid.RowDefinitions>
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
        <RowDefinition Height="auto" />
    </Grid.RowDefinitions>

    <Grid.ColumnDefinitions>
        <!-- 6% -->
        <ColumnDefinition Width="0.6*" />
        <!-- 47% -->
        <ColumnDefinition Width="*" />
        <!-- 47% -->
        <ColumnDefinition Width="*" />        
    </Grid.ColumnDefinitions>

    <controls:UCBusy Grid.Row="1" Grid.RowSpan="12"
                     Grid.ColumnSpan="3"
                     Panel.ZIndex="100" 
                     Visibility="Visible"
                     Width="auto" Height="auto"/>

    <!-- here grid components -->

 </Grid>
</UserControl>