I've got this code:

```
<GroupBox Style="{DynamicResource MaterialDesignCardGroupBox}" Grid.Row="0" Grid.Column="0" >
    <Label Content="{Binding MatchController.Match.TeamHome}" />
    <GroupBox.HeaderTemplate>
        <DataTemplate>
            <StackPanel Orientation="Horizontal">
                <Image Height="32" Width="32" Source="{Binding MatchController.Match.TeamHomeShield}" />
                <Label Content="{Binding MatchController.Match.TeamHome}" />
                <TextBlock Margin="8,0,0,0" VerticalAlignment="Center" Style="{StaticResource MaterialDesignSubheadingTextBlock}" Text="{Binding Match.TeamHome}"/>
            </StackPanel>
        </DataTemplate>
    </GroupBox.HeaderTemplate>
</GroupBox>

```

As you can see I've got a header template with a DataTemplate inside the GroupBox. The strange thing is the Label outside the GroupBox displays the value of TeamHome correctly however inside the StackPanel in the DataTemplate nothing is displayed and the binding is the same, why? Mystery of the life.