What is missing that I get an NS_BASE_STREAM_CLOSE

I just recently joined a website project. In order to work on it, I cloned the git repo and set up a fresh LEMP stack on a VPS to serve the page. It took a surprising amount of work to get the thing running (my first attempt had been on a laptop on it wouldn't even serve the first index.php properly). I've now got it to show the homepage and everything but a font seems to load up alright.

There are a number of links that go to dynamically generated pages. On the final product, these will be created with fresh data; for now the data is just pulled from a database so that we can tweak how it's displayed. My problem is these pages won't bloody load. It doesn't matter if I try this in Firefox, Chrome, Brave, or Konqueror, on Windows 7, Fedora, or Debian.

Wactching FF's dev tools, the server approves the request and serves the page (code 200), but nothing is rendered on the page (blank white screen) and nothing shows up in the console. Even the JS debugger won't show anything unless I run a JS based extension like AdBlock Ultimate. If I have AdBlock running, the page's name shows up under Sources and the only error in there is this:

    Error loading this URL: Could not load the source for http://dubyahdubyah/reports/view/506.
[Exception... "Component returned failure code: 0x80470002 (NS_BASE_STREAM_CLOSED) [nsIInputStream.available]"  nsresult: "0x80470002 (NS_BASE_STREAM_CLOSED)"  location: "JS frame :: resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/shared/DevToolsUtils.js :: onResponse :: line 453"  data: no]
Stack: onResponse@resource://gre/modules/commonjs/toolkit/loader.js -> resource://devtools/shared/DevToolsUtils.js:453:23
onStopRequest@resource://gre/modules/NetUtil.jsm:128:17
Line: 453, column: 0

I've been googling all day and I'm tired of beating my head against the keyboard.

Had the same problem with FireFox 55.0.2: a single site/page wasn't working whereas other sites were fine.

I tried multiple things such as: disabling Firefox extensions, removing cookies, which didn't work. But the problem didn't appear under a different Firefox profile. The built-in web developer tools showed that the webpage responded with a HTTP 200 and was loaded from cache.

I then cleared the cache and the page was working again. So maybe the cache was corrupted somehow.