Solved setting CacheMode
to the Grid
elements.
For Example:
<Grid Height="70" CacheMode="BitmapCache" Grid.Row="0" VerticalAlignment="Top">
<Grid.Background>
<LinearGradientBrush EndPoint="0.5,1" StartPoint="0.5,0">
<GradientStop Color="#FF1665CD" Offset="1"/>
<GradientStop Color="#FF5395EC"/>
</LinearGradientBrush>
</Grid.Background>
<Primitives:PivotHeadersControl x:Name="HeadersListElement"/>
</Grid>