The 'Access-Control-Allow-Origin' header contains multiple values '*, *', but only one is allowed.

[proven leaf]

In my project, I'm running a fetch function. I've made it under a library component in the folder /library/data.js and it looks like this:

export async function GetData(query, variables) {

    const { data } = await fetch(process.env.NEXT_PUBLIC_GRAPHQL_URL, {
    
        method: 'POST',
        headers: { 'Content-Type': 'application/json' },
        body: JSON.stringify({ query, variables }),
        next: { revalidate: parseInt(process.env.REVALIDATE_TIME) },
    
    }).then((res) => res.json());

    return data;

}

Now this query seems to work for pretty much everything, building pages and all. However, although I had it working previously and nothing has changed about this component, it's decided that search functionality isn't going to work.

I've got a Search Page, which currently looks like this:

import SearchBox from "@/components/search/searchBox";
import SearchResults from "@/components/search/searchResults";
import { GetData } from "@/lib/data";
import { useRouter } from "next/router";
import { useEffect, useState } from "react";
import { SEARCH_RESULTS } from "@/data/search";

const GetResults = async (query) => {
    const data = await GetData(SEARCH_RESULTS, { search: query });
    const values = Object.values(data);
    const results = [];
    values.forEach((value) => {
        if(value.edges.length) {
            results.push(value.edges);
        }
    });
    // flatten the array
    const flatResults = [].concat.apply([], results);
    return flatResults;
};

const SearchPage = () => {
    const router = useRouter();
    const { query } = router.query;

    const [results, setResults] = useState([]);

    useEffect(() => {
        setResults([]);
        if (query) {
            GetResults(query).then((res) => {
                setResults(res);
            });
        }
    }, [query]);

    return (
        <div>
            <h1>Search</h1>
            <SearchBox className={'bg-black text-white border border-white rounded-md px-2 py-1'} />
            <SearchResults results={results} query={query} />
        </div>
    )
}

export default SearchPage;

The <SearchBox /> is just an input that handles Debouncing and the pathname of the page, and the <SearchResults /> just helps flatten the array of the results.

But now when I attempt to run this, I get an error as pictures below:

[smoky wasp]

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[proven leaf]

I can confirm that the issue is there, as the preflight suggests:

But I don't know how to fix this or why this even started appearing in the first place? It was literally working a day or two ago, and as far as I can see through the branch history nothing has changed. When I check through previous Vercel deployments, I still can't access search results.