Sporadic CORS errors

Hi, I have a weird situation that's been happening for about a year now. Every now and then, for some minutes, all requests who need a preflight request fail, because out of nowhere the 'access-control-allow-...' headers are missing.

I tried restarting the server, clearing the cache, messing around with the order and content of the cors middleware and the headers, and I've found no fix. The only solution is to just come back about 30 minutes later and send the requests again. Only then they start working again.

The only thing I've noticed, is that the headers are back again only if the origin doesn't match. For example, if I put some invalid domain in the 'Access-Control-Allow-Origin' header. But if the headers are correct and matching what needs to match, then they disappear, only to appear again some 30 minutes later.

Having such a sporadic behaviour, and most of the time working correctly, it's been very frustrating and hard to identify why this is happpening. Does anyone have any ideas? I'm using Laravel 7.3.0 as back-end and NuxtJs with Axios as front-end. I'm also using Cloudflare and Docker.

namespace App\Http\Middleware;

use Closure;
use Sentry\Laravel\Facade;

class Cors
{
    /**
     * Handle an incoming request.
     *
     * @param  \Illuminate\Http\Request  $request
     * @param  \Closure  $next
     * @return mixed
     */
    public function handle($request, Closure $next)
    {
        $response = $next($request);

        //In case of avatars, header() is not StreamedResponse function.
        if ($response instanceof \Symfony\Component\HttpFoundation\StreamedResponse) {
            return $response;
       }

        $IlluminateResponse = 'Illuminate\Http\Response';
        $SymfonyResponse = 'Symfony\Component\HttpFoundation\Response';
        $JsonResponse = 'Illuminate\Http\JsonResponse';

        $headers = [
            'Access-Control-Allow-Origin' => "*",
            'Access-Control-Allow-Methods' => 'POST, GET, OPTIONS, PUT, PATCH, DELETE',
            'Access-Control-Allow-Headers' => 'Access-Control-Allow-Headers, Origin,Accept, X-Requested-With, Content-Type, Access-Control-Request-Method, Authorization , Access-Control-Request-Headers',
            'Access-Control-Allow-Crendentials' => 'true'
        ];

        if($response instanceof $IlluminateResponse || $response instanceof $JsonResponse) {
            foreach ($headers as $key => $value) {
                $response->header($key, $value);
            }
            return $response;
        }

        if($response instanceof $SymfonyResponse) {
            foreach ($headers as $key => $value) {
                $response->headers->set($key, $value);
            }
            return $response;
        }

        return $response;
    }
}