400 error from POST request

Hi! We build some project and shared to our customers. Now we found mistake in our curl request on source. Our curl request have a param
curl_setopt($curl, CURLOPT_POST, 1);
this is param don’t need in request but we can’t remove him from most website of customer projects. When we adding our website to CF our API have many fail requests because 400 error answered cross CF. How we can getting this error to control in our server and change status code from customer to 200 and return correct data. Our API url didn’t have self subdomain and work in main domain in folder. We can’t redirecting request to another subdomain because CF bloking request with 400 code(client sent invalid “Content-Length” header while reading client request headers) before redirecting.