Tabbed page does not show more than 3 icons/titles

I have a simple TabbedPage with 4 children, all in XAML. When I run this on iOS or Android the 4th child is not visible although it is there and I can click on it. The same occurs if I a change the childrens' order. It is always the last child in the list that has no visual representation if I use 4 or more children.

• On iOS (device and simulator) I don't see anything at all (but can click on this "nothing" as if it were there).
• On Android I see the thin white line at bottom of the tab bar after clicking.

I duplicated the 4th entry for testing: Now I have the same thing with 4 out of 5 entries. It is working as expected if I use 3 children.
Is there any limitation on 3 icons or is it a bug?
What am I doing wrong?

I use the latest Xamarin Forms (2.5.0.122203) with Rider and Visual Studio for Mac
Here is my MainPage.xaml:

<TabbedPage ...>
   <TabbedPage.Children>
       <NavigationPage Title="Browse">
           <NavigationPage.Icon>
               <OnPlatform x:TypeArguments="FileImageSource">
                   <On Platform="iOS" Value="tab_feed.png"/>
               </OnPlatform>
           </NavigationPage.Icon>
           <x:Arguments>
               <views:ItemsPage />
           </x:Arguments>
       </NavigationPage>

       ...

       <NavigationPage Title="Settings">
           <NavigationPage.Icon>
               <OnPlatform x:TypeArguments="FileImageSource">
                   <On Platform="iOS" Value="tab_settings.png"/>
               </OnPlatform>
           </NavigationPage.Icon>
           <x:Arguments>
               <views:SettingsPage />
           </x:Arguments>
       </NavigationPage>
   </TabbedPage.Children>
</TabbedPage>