Back button behaves strange when putting a tabbed page inside a NavigationPage on UWP

Description

When trying to integrate the tabbed page in our application. We wanted to give the user the ability to navigate outside of the tabbed page for a full screen experience. On UWP a weird behavior occurs when navigating between the tabs and while navigating inside of them. Each of our tabs is a navigation page that hosts a stack of views the user can go to and back. It happens on XF 3.1 which we took so we could have the tabbed page on bottom for android.

Steps to Reproduce

1. Open/run the sample application
2. Click on go to the tab page button
3. Then while in the first tab click go to another page
4. Go to second tab
5. Go back to the first tab

Expected Behavior

The back button should be visible allowing the user to go back in that navigation stack.

Actual Behavior

The back button isn't visible

Basic Information

• Version with issue: 3.1.0.583944
• Last known good version:
• IDE: Visual Studio Professional 2017 15.7.2
• Platform Target Frameworks:
  • UWP: 10.0.16299.0
• Android Support Library Version:
• Nuget Packages:
• Affected Devices:

Screenshots

Reproduction Link

https://github.com/devqasm/TabbedPageSample