lighthouse Timed out waiting for fetched start_url

I have a website that includes a manifest.json in the root of the domain.

/manifest.json (for content see below)

Scenarios

When I check the google lighthouse audit it works on the homepage.
When I check it on a suburl (like /test/) the message from lighthouse (under PWA) is: Timed out waiting for fetched start_url. I don't change the start_url for each subpage because I want that the start_url is always the homepage.

Does anybody knows why lighthouse is complaining and how I can fix it?

Content of manifest.json

{
  "name": "My website",
  "short_name": "My website",
  "start_url": "/",
  "icons": [
    {
      "src": "/assets/favicons/android-chrome-192x192-0eb7305556625ca6988c1f745f8de22ce1de04bdee9c129f8a04bf727dd4e23c.png",
      "sizes": "192x192",
      "type": "image/png"
    },
    {
      "src": "/assets/favicons/android-chrome-512x512-b5a1336abb27251a9b2baefc0a2789cd1fd8d644c9d8e006744f02daa323ab68.png",
      "sizes": "512x512",
      "type": "image/png"
    }
  ],
  "theme_color": "#ffffff",
  "background_color": "#ffffff",
  "display": "standalone"
}

response headers of manifest.json

alt-svc: clear
cache-control: private, max-age=0, no-cache
content-encoding: gzip
content-type: application/json
date: Mon, 18 Mar 2019 15:36:50 GMT
last-modified: Thu, 14 Mar 2019 12:54:03 GMT
server: nginx
status: 200
status: 200 OK
vary: Accept-Encoding
via: 1.1 google
x-request-id: 9eeb9731-9db0-43c8-bc98-9fed8a76fda2
x-runtime: 0.003905

Upvotes: 1