TabControl is always the last one to receive focus when using Tab key navigation

[shinywong]

Describe the bug
TabControl is always the last one to receive Tab focus, no matter where it was placed in the XAML file, and no matter which value its TabIndex was set.

To Reproduce
Steps to reproduce the behavior:

1. XAML file snippet:

<StackPanel>
    <StackPanel>
        <Button Content="Button A"/>
        <TabControl>
            <TabItem Header="Tab">
                <Button Content="Button B"/>
            </TabItem>
        </TabControl>
    </StackPanel>
    <Button Content="Button C"/>
</StackPanel>

2. Navigate using Tab key, you will find out the actual Tab order is
   "Button A" -> "Button C" -> "Button B".

Expected behavior
The Tab order should be "Button A" -> "Button B" -> "Button C".
Without using MahApps.Metro, it will work as expected.

Screenshots
(None)

Environment

• MahApps.Metro: v1.6.5
• OS: Win10 1909
• Visual Studio: 2019 16.5.0
• .NET Framework: 4.8

Repo
(None)

Additional context
(None)

[punker76]

@shinywong I can't reproduce this with the current source. So I'll close this for now. But feel free to re-open this, if you are still get this issue with the latest version.