Xamarin Forms with a NavigationPage repeat view at bottom of screen on Nexus 5

Hi there. When I test some of the Xamarin forms samples and my own app on my Nexus 5, the view stops before the bottom of the screen and then starts to repeat itself.

Code:

using System;
using Xamarin.Forms;

    namespace ToDoList
    {
        public class App
        {
            public static Page GetMainPage ()
            {   
                return new NavigationPage(new HomeScreen());
            }
        }
    }

<?xml version="1.0" encoding="UTF-8"?>
<ContentPage    xmlns="http://xamarin.com/schemas/2014/forms" 
                xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml" 
                x:Class="ToDoList.HomeScreen"
                Padding="20"
                Title="My Activities">
    <ContentPage.Content>
        <StackLayout Spacing="10"
               VerticalOptions="CenterAndExpand" 
               Orientation="Vertical">
            <Label Text="Stop"
                   BackgroundColor="Red"
                   Font="20" />
            <Label Text="Slow down"
                   BackgroundColor="Yellow"
                   Font="20" />
            <Label Text="Go"
                   BackgroundColor="Green"
                   Font="20" />
            <Label Text="Stop"
                   BackgroundColor="Red"
                   Font="20" />
            <Label Text="Slow down"
                   BackgroundColor="Yellow"
                   Font="20" />
            <Label Text="Go"
                   BackgroundColor="Green"
                   Font="20" />
        </StackLayout>
    </ContentPage.Content>
</ContentPage>

using System;
using System.Collections.Generic;
using Xamarin.Forms;

namespace ToDoList
{   
    public partial class HomeScreen : ContentPage
    {   
        public HomeScreen ()
        {
            InitializeComponent ();
        }
    }
}

Once, it rendered taking up less than the full screen but without repeating.

If I delete the navigation page and just have a ContentPage alone, it renders correctly. See images below. Is this a bug?