Sorry, I have never seen this before.

Looking at the output of cURL against this, it only sends but a single, simple script tag; so that is quite incorrect HTML from the get go.

Taking a look at this in the browser console, shows the same incorrect HTML. The event listener did seemingly fire, I can see a response from `.../client/` as requested in the fetch() call:

https://void.cat/d/FaoVfeC6dYnusT8eqUskK5.webp

But aside from that, no error is shown. I didn't disable my adblock and my browser is Opera GX (which is usually also a source of troubble on it's own...).

Sorry, this is all I could figure out ^^'