Webview: the viewport does not position correctly when I focus on a field and the keyboard appears

Bug Reports
1

Fuse 1.8.1 Sierra IOS 11.3.x
I have a webview pointing to this site http://www.chepizza.it/chat

<App>
	 <DockPanel>
        <StatusBarBackground Dock="Top"/>
        <NativeViewHost>
            <WebView Dock="Fill" Url="http://www.chepizza.it/chat">
            </WebView>
        </NativeViewHost>
        <BottomBarBackground Dock="Bottom"/>
    </DockPanel>
</App>

The viewport does not position correctly when I focus on a field and the keyboard appears

You can look at the problem in more detail in this video:

In the first part of the video you can see the problem, in the second part of the video video I opened the same page with the browser of the device to show you that the keyboard works correctly

2

I resolved by deleting the tags StatusBarBackground and BottomBarBackground