Angular 2 routing sometimes fails after 1-2 minutes of activity in the application

I have a .NET Core + Angular 2 / Typescript / SystemJS app. And use lazy loading to load modules

Here is the app-routing.module.ts :

import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';

const routes: Routes = [
    { path: '', loadChildren: 'app/dashboard/dashboard.module#DashboardModule' },
    { path: 'signup', loadChildren: 'app/signup/signup.module#SignUpModule' },
    { path: 'signin', loadChildren: 'app/signin/signin.module#SignInModule' },
    { path: 'welcome', loadChildren: 'app/welcome/welcome.module#WelcomeModule' },
];

@NgModule({
    imports: [RouterModule.forRoot(routes)],
    exports: [RouterModule]
})
export class AppRoutingModule { }

      

        
        
        
      

    

And welcome-routing.module.ts :

import { NgModule } from '@angular/core';
import { RouterModule, Routes } from '@angular/router';

import { AuthGuard } from './../providers/auth-guard.service';

import { WelcomeComponent } from './welcome.component';

const welcomeRoutes: Routes = [
    { path: '', component: WelcomeComponent, canActivate: [AuthGuard] }
];

@NgModule({
    imports: [RouterModule.forChild(welcomeRoutes)],
    exports: [RouterModule]
})
export class WelcomeRoutingModule { }

      

        
        
        
      

    

So when I logged in and went to the control panel page http://example.com/ . Then there is no activity in the web application for about 1-2 minutes and then click on the welcome page. I sometimes have an error (sometimes the page loads correctly):

zone.min.js:1 GET http://example.com/app/welcome/welcome.module.js 500 (Internal Server Error)


core.umd.min.js:13 ERROR Error: Uncaught (in promise): Error: (SystemJS) XHR error (500 Internal Server Error) loading http://example.com/app/welcome/welcome.module.js
Error: XHR error (500 Internal Server Error) loading http://example.com/app/welcome/welcome.module.js

      

        
        
        
      

    

And when I paste the url http://example.com/app/welcome/welcome.module.js into the browser

I have an error in the console:

Failed to load resource: the server responded with a status of 500 (Internal Server Error)

      

        
        
        
      

    

After I hit "hard reload" everything is fine. The server side seems to be working correctly. I cannot figure out the reason for the error.

Lazy loading? SystemJS loading modules incorrectly? Or something else? How to solve this random problem?