Empty css/js on 1 page (files loading as "/")

Problem/Motivation

Similar to https://www.drupal.org/project/advagg/issues/3224986 🐛 Missing/empty CSS only on one page Closed: won't fix .

I have about 50+ sites (all use the same theme and have the same features). For some reason, on 1 of them (and only 1) there is a page on the backend where the js/css doesn't load. It's not all js/css files, just a few.

No errors on the network tab at all. If I view the page source, I see this:

<link rel="stylesheet" media="all" href="/sites/site_name_here/files/css/css_saumSBT-sE-epVDsaGD_wRDyJsLJxltrrNWevT73B_0.css" />
<link rel="stylesheet" media="all" href="/" />
<link rel="stylesheet" media="all" href="/sites/site_name_here/files/css/css_gpfh12_OvpJ8ZFCmnKFFkUVpZ1oWi6EEQv21ayue98Y.css" />

Near the bottom of the page I have this:

<script src="/"></script>
<script src="/modules/contrib/ckeditor/vendor/ckeditor.js?v=4.18.0"></script>
<script src="/"></script>

The other working sites show this:

<script src="/sites/site_name_here/files/js/js_Nf02DGL_nxHn7rSaR3QmNX3OiR6D5PYk35zhbuakjzM.js"></script>
<script src="/modules/contrib/ckeditor/vendor/ckeditor.js?v=4.18.0"></script>
<script src="/sites/site_name_here/files/js/js_xalgGszc7jHHMkHnQlXr4FVAq0LRapWIH0xH8KNZF80.js"></script>

I do however see these errors in the console:
"Refused to apply style because its MIME type ('text/html') is not a supported stylesheet MIME type, and strict MIME checking is enabled."
"Refused to execute script because its MIME type ('text/html') is not executable, and strict MIME type checking is enabled."

Which I guess makes sense because of the "/". So no stylesheet/js file is being loaded.

I'm almost positive clearing the cache would work. I'm just more concerned with the how or why this happened.

Perhaps this isn't even an advagg issue either. I'm just looking for an answer as to what could have caused this to occur.

Any ideas? Thanks!