Unexpected 404 logs on every page refresh (middleware removed, still occurring)

[ttrBetter]

Hi everyone,

I’m running into an issue where every page refresh logs a 404 Not Found error, even though the actual page renders correctly. This happens on all routes.

What’s happening:

When I refresh a page, the application logs a 404 error.

The browser shows the correct page (not a 404 screen).

This happens consistently on all pages, not just specific routes.

What I’ve tried:

Removed my custom middleware → the error still occurs.

Attached a debugger → saw an E394 error.

Verified that the rendered page content is correct, only the logs are wrong.

Problem:
It seems like the request/response cycle is triggering a 404 internally, but then still rendering the expected page. I suspect something related to middleware ordering, client-side routing, or static assets, but I haven’t been able to pinpoint it.

Question:

Has anyone seen similar behavior, where the server logs 404s on refresh but still renders the correct page?

Could this be due to catch-all routing for a frontend framework, or a logging middleware misreporting status codes?

Any tips on how to debug the E394 error further?

Thanks in advance for any insights! 🙏

[icyJoseph]

Is the status code in the response 200 too? Strange indeed, could you give us some more context on the issue?

[verheyenkoen]

Don't know if this is in any way relevant to your case but I've seen this error "E394" recently because of a bug in my useEffect cleanup callback. I had written my own hook that attaches event listeners to an element ref and detaches it again using an AbortController. It basically did this:

useEffect(() => {
    if (elementRef.current) {
      const abortController = new AbortController();

      elementRef.current.addEventListener(
        eventName,
        eventHandler as EventListenerOrEventListenerObject,
        {
          signal: abortController.signal,
        },
      );

      return abortController.abort;
    }
  }, [elementRef, eventName]);

This failed whenever a Next.js redirect caused the component that used the hook to unmount. Turns out returning abortController.abort here as the cleanup function caused this. Fixed it by changing this line to:

return () => abortController.abort();

I assumed since the cleanup function and the abort method both accepted not arguments, this should work but maybe the React compiler does some "magic" or memoization here that breaks that.