UWP ExtendedExecution - Error when requesting Extended Execution

I have a UWP application that requests Extended Execution in a callback that gets fired after an operation starts like below:

private async void HandleOnSyncStart(ISyncStart msg)
{
    // request extended execution
    ExtendedExecutionResult result = await 
      Utils.ExtendedExecutionHelper.RequestExtendedExecutionSessionAsync();
}

, but I get following error

The group or resource is not in the correct state to perform the 
 requested operation. (Exception from HRESULT: 0x8007139F)

The error is thrown on return call in RequestExtendedExecutionSessionAsync() method shown below. This is the stacktrace:

   at Windows.ApplicationModel.ExtendedExecution.ExtendedExecutionSession..ctor()
   at MyProject.UWP.Utils.ExtendedExecutionHelper.<RequestExtendedExecutionSessionAsync>d__0.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.CompilerServices.TaskAwaiter.ThrowForNonSuccess(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()
   at MyProject.UWP.MainPage.<HandleOnSyncStart>d__65.MoveNext()

The extended execution session is requested in RequestExtendedExecutionAsync() method of ExtendedExecutionHelper static class like below:

    public static async Task<ExtendedExecutionResult> RequestExtendedExecutionSessionAsync()
    {
        ClearExtendedExecutionSession();  //first clear if any session granted

        var newSession = new ExtendedExecutionSession();
        newSession.Reason = ExtendedExecutionReason.Unspecified;
        newSession.Description = "Extended Execution Request";
        newSession.Revoked += OnExtendedExecutionSessionRevoked;

        ExtendedExecutionResult result = await newSession.RequestExtensionAsync();
        switch (result)
        {
            case ExtendedExecutionResult.Allowed:
                Debug.WriteLine(string.Format("ExtendedExecutionHelper: ExtendedExecution allowed."));
                session = newSession;
                break;
            case ExtendedExecutionResult.Denied:
                Debug.WriteLine(string.Format("ExtendedExecutionHelper: ExtendedExecution denied."));
                newSession.Dispose();
                break;
        }

        return result; //ERROR
    }

This exception is thrown in the constructor of ExtendedExecutionSession class.

Stacktrace: at Windows.ApplicationModel.ExtendedExecution.ExtendedExecutionSession..ctor()

And this exception can be caused by

Only one ExtendedExecutionSession can be requested at any time; attempting to create another session while one is currently active will cause an exception to be thrown from the ExtendedExecutionSession constructor.

So it looks like ClearExtendedExecutionSession fails to dispose of a previous running session. If your code is adopted from this page... maybe the code has some subtle bugs, as indicated in some comments on that page.

You could show how you deal with the previous running session.