A GET (or DELETE) request can never contain a request body, it only supports query parameters. multipart/form-data is always sent in the request body. This means that you cannot use GET or DELETE, but only use POST or PUT.
If POST requests are stalled, you need to figure out where. Do a POST to a simple PHP page which only prints out $_SERVER, $_GET, $_POST and $_FILES. That way you can see if the request is successfully received by the server or not. If you see output, then the problem is more likely to be in the PHP code. If you see incorrect output, then the problem is more likely to be in the sending code.