Textbox focus does not work - wpf

Question

I am using VS2015 and currently I am under pressure of this issue and I don't know why it's not working on VS2015.
I do have a "Splash Screen" which is a welcome page and after that will be another page to show some other forms. I do have 5 borders represent as a container, each border will show after hit next and all of the borders are place only in the same View which is MainWindow.xaml.
Every field just like Name textbox field do have a Validation.ErrorTemplateand I am not sure if that will affect the textbox focus.
I used FocusManager.FocusedElement and text1.focus() but still not working and other solution coming from other people having similar issues but still not working in my end.
I am guessing something in logical focus but when I force to focus the textbox still not working.
Simple example of XAML.
<Border x:Name="Panel1" Opacity="0" IsHitTestVisible="False"
RenderTransformOrigin="0.5,0.5">
<Border.RenderTransform>
<TransformGroup>
<ScaleTransform />
<SkewTransform />
<RotateTransform />
<TranslateTransform Y="515" />
</TransformGroup>
</Border.RenderTransform>
<Grid Background="{DynamicResource ActiveBrush}">
<ScrollViewer Margin="0,10,0,76.33" Height="450" Width="630" VerticalAlignment="Top"
VerticalScrollBarVisibility="Auto"
Template="{DynamicResource ContentPanelScrollviewerStyle}">
<StackPanel Orientation="Vertical" Width="630">
<Label Content="Name" HorizontalAlignment="Left"
VerticalAlignment="Top"
FontSize="{DynamicResource FieldGroupHeadingTextSize}"
Foreground="{DynamicResource TextBrush}" />
<Grid Height="170">
<Grid.ColumnDefinitions>
<ColumnDefinition Width="*"></ColumnDefinition>
<ColumnDefinition Width="*"></ColumnDefinition>
</Grid.ColumnDefinitions>
<Grid Column="0" IsVisibleChanged="Grid_IsVisibleChanged">
<StackPanel>
<Label Content="Name"
HorizontalAlignment="Left"
VerticalAlignment="Top"
FontSize="{DynamicResource FieldLabelTextSize}"
Foreground="{DynamicResource TextBrush}" />
<TextBox Name="text1" Validation.ErrorTemplate="{StaticResource validationTemplate}"
HorizontalAlignment="Left" TextWrapping="Wrap"
Text="{Binding Name, NotifyOnValidationError=True}"
VerticalAlignment="Top" Width="298.8" Height="24"
FontSize="{DynamicResource FieldInputTextSize}"
Foreground="{DynamicResource TextBrush}">
<i:Interaction.Behaviors>
<behaviors:ReadOnlyWhileValidatingBehavior />
</i:Interaction.Behaviors>
</TextBox>
</StackPanel>
</Grid>
</Grid>
</StackPanel>
</ScrollViewer>
</Grid>
</Border>