Why is Angular component not loading on browser back/forward navigation?

Question

Angular 7.2.13

When navigating with the browser back button, the HTML of the component is loaded, but the component css/js is not loaded, and the page hangs.

However loading works fine when navigated by a link click or router.navigateByUrl() or if the page is reloaded. But never when navigating with the forward/back button.

I'm getting no console errors.

It works perfectly on the development server http://localhost:4200/. This issue occurs only in production.

UPDATE

This is happening in a child route.

UPDATE 2

Can't replicate the issue in a stackblitz with the same route structure. https://angular-tpsr5z.stackblitz.io/.

UPDATE 3

When it hangs both the previous and the new route html are shown.

After hanging like this the component will immediately load if I click anything that fires a component method, or changes a property of the component.

UPDATE 4

Package Json

{
  "name": "tuilder-ng",
  "version": "0.0.0",
  "scripts": {
    "ng": "ng",
    "start": "ng serve",
    "build": "ng build",
    "test": "ng test",
    "lint": "ng lint",
    "e2e": "ng e2e"
  },
  "private": true,
  "dependencies": {
    "@angular/animations": "^7.2.13",
    "@angular/cdk": "^7.3.7",
    "@angular/common": "^7.2.13",
    "@angular/compiler": "^7.2.13",
    "@angular/core": "^7.2.13",
    "@angular/forms": "^7.2.13",
    "@angular/http": "^7.2.13",
    "@angular/material": "^7.3.7",
    "@angular/platform-browser": "^7.2.13",
    "@angular/platform-browser-dynamic": "^7.2.13",
    "@angular/router": "^7.2.13",
    "@ecodev/fab-speed-dial": "^3.1.0",
    "@google/markerclustererplus": "^2.1.11",
    "@swimlane/ngx-charts": "^10.1.0",
    "@types/googlemaps": "^3.30.19",
    "@types/lodash": "^4.14.123",
    "chart.js": "^2.8.0",
    "core-js": "^2.6.5",
    "lodash": "^4.17.11",
    "moment-timezone": "^0.5.23",
    "ng2-charts": "^1.6.0",
    "ngx-material-timepicker": "^2.13.0",
    "ngx-order-pipe": "^2.0.2",
    "rxjs": "^6.4.0",
    "thenby": "^1.3.0",
    "zone.js": "^0.8.29"
  },
  "devDependencies": {
    "@angular-devkit/build-angular": "^0.13.8",
    "@angular/cli": "^7.3.8",
    "@angular/compiler-cli": "^7.2.13",
    "@angular/language-service": "^7.2.13",
    "@types/jasmine": "^3.3.12",
    "@types/jasminewd2": "~2.0.6",
    "@types/node": "^10.12.30",
    "codelyzer": "~4.5.0",
    "jasmine-core": "~3.3.0",
    "jasmine-spec-reporter": "~4.2.1",
    "karma": "^4.1.0",
    "karma-chrome-launcher": "~2.2.0",
    "karma-coverage-istanbul-reporter": "^2.0.5",
    "karma-jasmine": "~2.0.1",
    "karma-jasmine-html-reporter": "^1.4.0",
    "protractor": "^5.4.2",
    "ts-node": "^8.0.3",
    "tslint": "~5.12.1",
    "typescript": "3.2.4"
  }
}

Server Redirect .htaccess

RewriteEngine On

RewriteCond %{HTTPS} off
RewriteRule .* https://%{HTTP_HOST}%{REQUEST_URI} [L,R=301]

Options +FollowSymLinks
DirectoryIndex index.html

RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule ^[a-zA-Z0-9-_.\/]+$ index.html

UPDATE 5

Cut down demo of the issue: https://ngtest.emanweb.design/

Answer 1

The issue was resolved by turning off ModPagespeed in Nginx for that particular domain.

pagespeed Disallow "https://*example.com/*";

ModPagespeed was interacting in some way with Angular to cause this weird behaviour.

Alternatively pagespeed can be turned off per url by appending: ?ModPagespeed=off