TabbedPage renders multiple times in Xamarin Forms using shell - forms

Question

I have a problem using TabbedPages in my Xamarin.Forms mobile app (Shell).
When I navigate to a TabbedPage containing 3 tabs, the 3 tabs are crunched up and repeating themselves all down the page.
To replicate it I:
Created a standard Xamarin Forms Shell app in Visual Studio 2019 Version 16.4.5
Upgraded to Xamarin Forms 4.4.0.991640
Added a TabbedPage and changed the navigation of the About button to navigate to the TabbedPage instead.
Here is a photo of how it looks on my android phone
If I remember correctly it also happened when I deployed to my iPhone.
Update due to Jason's comment
All the code is automatically generated by Microsoft, my only interaction was to add an empty TabbedPage and change a line of code in AppShell.xaml.
(Note - while not relevant to this particular demo, I also got the same issue when navigating from a ListView in a ContentPage in my Xamarin.Forms app.)
Added TabbedPage1.xaml:
<?xml version="1.0" encoding="utf-8" ?>
<TabbedPage xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
x:Class="App1.Views.TabbedPage1">
<!--Pages can be added as references or inline-->
<ContentPage Title="Tab 1" />
<ContentPage Title="Tab 2" />
<ContentPage Title="Tab 3" />
</TabbedPage>
Added TabbedPage1.xaml.cs:
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using Xamarin.Forms;
using Xamarin.Forms.Xaml;
namespace App1.Views
{
[XamlCompilation(XamlCompilationOptions.Compile)]
public partial class TabbedPage1 : TabbedPage
{
public TabbedPage1()
{
InitializeComponent();
}
}
}
Amended AppShell.xaml (all I did was change the line from DataTemplate local:AboutPage to DataTemplate local:TabbedPage1):
<?xml version="1.0" encoding="UTF-8"?>
<Shell xmlns="http://xamarin.com/schemas/2014/forms"
xmlns:x="http://schemas.microsoft.com/winfx/2009/xaml"
xmlns:d="http://xamarin.com/schemas/2014/forms/design"
xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
mc:Ignorable="d"
xmlns:local="clr-namespace:App1.Views"
Title="App1"
x:Class="App1.AppShell">
<!--
Styles and Resources
-->
<Shell.Resources>
<ResourceDictionary>
<Color x:Key="NavigationPrimary">#2196F3</Color>
<Style x:Key="BaseStyle" TargetType="Element">
<Setter Property="Shell.BackgroundColor" Value="{StaticResource NavigationPrimary}" />
<Setter Property="Shell.ForegroundColor" Value="White" />
<Setter Property="Shell.TitleColor" Value="White" />
<Setter Property="Shell.DisabledColor" Value="#B4FFFFFF" />
<Setter Property="Shell.UnselectedColor" Value="#95FFFFFF" />
<Setter Property="Shell.TabBarBackgroundColor" Value="{StaticResource NavigationPrimary}" />
<Setter Property="Shell.TabBarForegroundColor" Value="White"/>
<Setter Property="Shell.TabBarUnselectedColor" Value="#95FFFFFF"/>
<Setter Property="Shell.TabBarTitleColor" Value="White"/>
</Style>
<Style TargetType="TabBar" BasedOn="{StaticResource BaseStyle}" />
</ResourceDictionary>
</Shell.Resources>
<!-- Your Pages -->
<TabBar>
<Tab Title="Browse" Icon="tab_feed.png">
<ShellContent ContentTemplate="{DataTemplate local:ItemsPage}" />
</Tab>
<Tab Title="About" Icon="tab_about.png">
<ShellContent ContentTemplate="{DataTemplate local:TabbedPage1}" />
</Tab>
</TabBar>
<!-- Optional Templates
// These may be provided inline as below or as separate classes.
// This header appears at the top of the Flyout.
<Shell.FlyoutHeaderTemplate>
<DataTemplate>
<Grid>ContentHere</Grid>
</DataTemplate>
</Shell.FlyoutHeaderTemplate>
// ItemTemplate is for ShellItems as displayed in a Flyout
<Shell.ItemTemplate>
<DataTemplate>
<ContentView>
Bindable Properties: Title, Icon
</ContentView>
</DataTemplate>
</Shell.ItemTemplate>
// MenuItemTemplate is for MenuItems as displayed in a Flyout
<Shell.MenuItemTemplate>
<DataTemplate>
<ContentView>
Bindable Properties: Text, Icon
</ContentView>
</DataTemplate>
</Shell.MenuItemTemplate>
-->
</Shell>