Wix Burn Process not closed

Question

Hello I have custom bootstrapper application. All work fine, but when work is done and i close app process continuing to hang. I've noticed that when i tryed to recompile installer. I have code like this:

protected override void Run()
    {

        //MessageBox.Show("Run");
        // set the global message dispatcher
        Dispatcher = Dispatcher.CurrentDispatcher;

        // Create the model, view model and the view of the main window.
        // The view model handles the enitre ui.
        Model model = new Model(this);
        MainWindowViewModel viewModel = new MainWindowViewModel(model);
        MainWindow mainWindow = new MainWindow(viewModel);

        Engine.Detect();

        // Create a Window to show UI.
        Engine.Log(Microsoft.Tools.WindowsInstallerXml.Bootstrapper.LogLevel.Verbose, "Creating UI");

        Engine.CloseSplashScreen();

        mainWindow.Show();

        // run the threading dispatcher
        Dispatcher.Run();

        // Finalize the installation (with the finalResult) and quit the process.
        Engine.Quit(model.FinalResult);
    }

I've debugged it and certainly it calls the function Engine.Quit(0) every time. Sometimes it work fine but sometimes the process dosen't stop. There is no "Shutting down, exit code: " line in log. And i don't know why. Does anybody have an idea what i do wrong

I've noticed that it happens only when i modify two or more packages.