Проблема с app.MapWhen() в маршрутизации .NET Core для нескольких проектов Angular

Вот пример, который я начинаю с asp.net core webapi .net6.

Стартап.cs

public class Startup
{
    public void ConfigureServices(IServiceCollection services)
    {
        services.AddControllers();
        services.AddSpaStaticFiles(configuration =>
        {
            configuration.RootPath = "wwwroot";
        });
    }

    public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
    {
        if (env.IsDevelopment())
        {
            app.UseDeveloperExceptionPage();
        }

        app.UseHttpsRedirection();

        app.UseStaticFiles();
        app.UseSpaStaticFiles();

        app.UseRouting();

        app.UseAuthorization();

        app.MapWhen(context => !context.Request.Path.StartsWithSegments("/survey"), mainApp =>
        {
            mainApp.UseStaticFiles(new StaticFileOptions
            {
                FileProvider = new PhysicalFileProvider(Path.Combine(env.WebRootPath, "back")),
                RequestPath = ""
            });

            mainApp.UseSpa(spa =>
            {
                spa.Options.SourcePath = "wwwroot/back";
                spa.Options.DefaultPageStaticFileOptions = new StaticFileOptions
                {
                    FileProvider = new PhysicalFileProvider(Path.Combine(env.WebRootPath, "back")),
                };
            });
        });

        app.MapWhen(context => context.Request.Path.StartsWithSegments("/survey"), surveyApp =>
        {
            surveyApp.UseStaticFiles(new StaticFileOptions
            {
                FileProvider = new PhysicalFileProvider(Path.Combine(env.WebRootPath, "survey")),
                RequestPath = "/survey"
            });

            surveyApp.UseSpa(spa =>
            {
                spa.Options.SourcePath = "wwwroot/survey";
                spa.Options.DefaultPageStaticFileOptions = new StaticFileOptions
                {
                    FileProvider = new PhysicalFileProvider(Path.Combine(env.WebRootPath, "survey")),
                };
            });
        });

        app.UseEndpoints(endpoints =>
        {
            endpoints.MapControllers();
        });
    }
}

Моя структура проекта такова.

И код, показывающий проект.

console.info("Back Project JavaScript Loaded");

console.info("Survey Project JavaScript Loaded");

Тест