Angular nested routing with lazy loading issue

After trying it on many different ways, what worked for me was changing core-routing.module.ts to have a single route and including the lazy loaded modules as children inside it:

const routes: Routes = [
  {
    path: '',
    component: CoreComponent,
    children: [
      { path: '', redirectTo: 'dashboard', pathMatch: 'full' },
      { path: 'dashboard', loadChildren: '../dashboard/dashboard.module#DashboardModule', canLoad: [AuthGuard] },
      { path: 'customers', loadChildren: '../customers/customers.module#CustomersModule', canLoad: [AuthGuard] },
      { path: 'history', loadChildren: '../history/history.module#HistoryModule', canLoad: [AuthGuard] },
      { path: 'processing', loadChildren: '../processing/processing.module#ProcessingModule', canLoad: [AuthGuard] },
      { path: '**', redirectTo: 'dashboard' }
    ]
  }
];

Hope this may help someone trying to implement the same functionality.