[Bug] Device.IsInvokeRequired is not changing to false after running the method on mainthread

[ghost]

Description
When loading a page asynchronously to a secondary window using a dispatcher on button click.then after running the method on method in secondary window.the Device.IsInvokeRequired Property does not changing to false.

Note : Checked with latest Xamarin.Forms 5.0.0.2599-pre1(5.0.0 Service Release 15 Pre Release 1)

Steps to Reproduce
Click the button.
Click the CheckisOnMainthread button twice.
open output window

Sample
SecondWindow.zip

Expected Behavior
Device.isInvokeRequired should be false after running the method on Mainthread.

Actual Behavior
Device.IsInvokRequired remains true even after running on MainThread.

Screenshots

[ghost]

Hi team,
Any update regarding this