Android : How to close connection with Application Tethering in Android

Using Delphi XE6

I have these codes:

  procedure TMainForm.FormKeyUp(Sender: TObject; var Key: Word; var KeyChar: Char;
  Shift: TShiftState);
var
  FService : IFMXVirtualKeyboardService;
begin
  if Key = vkHardwareBack then
  begin
    TPlatformServices.Current.SupportsPlatformService(IFMXVirtualKeyboardService, IInterface(FService));
    if TVirtualKeyBoardState.Visible in FService.GetVirtualKeyBoardState then
    begin
      FService.HideVirtualKeyboard;
    end else
    begin
      if TabControl1.ActiveTab = TabItem2 then
      begin
        TabControl1.ActiveTab := TabItem1;
        Key := 0;
      end else
      begin
        Self.Hide;
        MainActivity.Finish;
        Application.MainForm.DisposeOf;
        Key := 0;
      end;
    end;
  end;
end;

procedure TMainForm.ConnectButtonClick(Sender: TObject);
begin
  TetheringManager1.Enabled:=True;
  TetheringAppProfile1.Enabled:=True;
  TetheringManager1.AutoConnect(3000);
end;

With hardware back button android app closes/opens okay when TetheringManager and TetheringAppProfiler is not enabled and not connected. But when connected then android app is not closing correctly and not opening correctly (I see only black screen, but next time app opens okay). Is there any way how I can disconnect tethering?