[Bug] Stepper incorrectly positions inside a Grid

Description

The top and bottom Steppers should be centered horizontally, but they start at the center position instead. I swapped a Button in to check, and that works fine.

Steps to Reproduce

<ScrollView xmlns="http://xamarin.com/schemas/2014/forms"
             xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
             BackgroundColor="White"
             x:Class="Xappy.Content.ControlGallery.ProppyControls.PaddingProperty">
    <Grid Margin="15">
        <Grid.RowDefinitions>
            <RowDefinition Height="40"/>
            <RowDefinition Height="*"/>
            <RowDefinition Height="40"/>
        </Grid.RowDefinitions>
        <Grid.ColumnDefinitions>
            <ColumnDefinition Width="100"/>
            <ColumnDefinition Width="*"/>
            <ColumnDefinition Width="100"/>
        </Grid.ColumnDefinitions>
        
        <Stepper Grid.Row="1"
                 Grid.Column="0"
                 VerticalOptions="Center"
                 />
        <Stepper Grid.Row="0" 
                 Grid.Column="1"
                 HorizontalOptions="Center"
        />
        <Stepper Grid.Row="1"
                 Grid.Column="2"
                 VerticalOptions="Center"
        />
        <Stepper Grid.Row="2"
                 Grid.Column="1"
                 HorizontalOptions="Center"
        />
        
        <Grid
            Grid.Row="1"
            Grid.Column="1"
            Margin="8"
            >
            <Grid.RowDefinitions>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
                <RowDefinition Height="*"/>
            </Grid.RowDefinitions>
            <Grid.ColumnDefinitions>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
                <ColumnDefinition Width="*"/>
            </Grid.ColumnDefinitions>

            
            <Frame HasShadow="False"
                   Grid.ColumnSpan="3"
                   Grid.RowSpan="3"
                   BorderColor="Red"
                   BackgroundColor="LightBlue">
            </Frame>
            
            <Label Grid.Row="1" Grid.Column="0" x:Name="LeftPadding" Text="0"  VerticalOptions="Center"/>
            <Label Grid.Row="0" Grid.Column="1" x:Name="TopPadding" Text="0" HorizontalTextAlignment="Center" />
            <Label Grid.Row="1" Grid.Column="2" x:Name="RightPadding" Text="0" VerticalOptions="Center" HorizontalOptions="End" />
            <Label Grid.Row="2" Grid.Column="1" x:Name="BottomPadding" Text="0" HorizontalOptions="Center" />
            
        </Grid>
    </Grid>
</ScrollView>

Basic Information

• Version with issue: 4.0-pre9
  • iOS: 12.2

Screenshots