Published Apps Script library has no contents anymore

Question

I've developed a GAS library called PssFleetData to access an API of mine in various Google sheets. This is my first time doing this and my experience with GAS and Javascript is limited (I've started using it only a couple weeks ago). In a few spreadsheet apps scripts, I've already used the library successfully before today. However when I'm trying to use it in a new project today, it is completely empty!

console.log(typeof(PssFleetData));
console.log(PssFleetData);
console.log(typeof(PssFleetData.Client));

produces

12:00:07    Info    object
12:00:07    Info    {}
12:00:07    Info    undefined

Client is actually a class with only static functions and the main entry point for the library.

• I've shared it to "everyone with a link" (see only).
• I've published a few versions.
• Yesterday I've started using clasp and VSCode to add proper JSDocs, generated the docs and put everything on github so the docs would show up on github pages (since the built-in Apps Script docs page is pretty useless). For that I've pulled the files via clasp, edited them and then pushed the changed files back to Apps Script, but didn't publish a new version yet.
• I'm using the same google account for all script development.
• I've given the new project the required permissions to run.

Today I tried using the library in a new script, added it just like before and selected the latest version (8). I've tried older versions which used to work, too, to no avail. Then I published a new version (9) and selected that in the new script project, but it still suffers from the same issue. The "developer snapshot" version doesn't work either.

Weirdly enough, the apps scripts I've written before today still work, no matter which version I choose (8, 9 or developer snapshot).

The script ID is: 1THzQ0jC6YrA2SyWMrHf1QauQdKYI4eMK4H-LhP6s1a9i5UvRa7p3TiaQ

Link to the github repo is: https://github.com/PSS-Tools-Development/pss-fleet-data-client-appsscript

The library's manifest file:

{
  "timeZone": "Etc/UTC",
  "dependencies": {},
  "exceptionLogging": "STACKDRIVER",
  "runtimeVersion": "V8",
  "oauthScopes": [
    "https://www.googleapis.com/auth/script.external_request"
  ]
}

The affected script's manifest file:

{
  "timeZone": "Etc/UTC",
  "exceptionLogging": "STACKDRIVER",
  "runtimeVersion": "V8",
  "dependencies": {
    "libraries": [
      {
        "userSymbol": "PssFleetData",
        "libraryId": "1THzQ0jC6YrA2SyWMrHf1QauQdKYI4eMK4H-LhP6s1a9i5UvRa7p3TiaQ",
        "version": "9",
        "developmentMode": false
      }
    ]
  },
  "oauthScopes": [
    "https://www.googleapis.com/auth/spreadsheets.currentonly",
    "https://www.googleapis.com/auth/script.external_request",
    "https://www.googleapis.com/auth/script.scriptapp"
  ]
}

Why is my GAS library merely an empty object now and how can I fix it?

_{I've already checked Troubleshooting script projects but didn't find a solution. Searching the web for things like google apps script library is undefined, google apps script library is empty, google apps script library no members, google apps script library is undefined no properties and others didn't yield anything useful either.}