InvalidArgument: null / Uploading picture to digital ocean space from webpage gives me an error

I’m trying to upload a picture to my Digital Ocean space. I made my own nodeJS server.

const {
  S3_ACCESS_KEY_ID,
  S3_SECRET_ACCESS_KEY,
  S3_ENDPOINT,
  S3_BUCKET,
} = require('./config');

const router = express.Router();

const s3 = new AWS.S3({
  accessKeyId: S3_ACCES_KEY_ID,
  secretAccessKey: S3_SECRET_ACCES_KEY,
  endpoint: S3_ENDPOINT,
  s3ForcePathStyle: true,
  signatureVersion: 'v4',
});

const upload = multer({
  storage: multerS3({
    s3: s3,
    bucket: S3_BUCKET,
    metadata: (req, file, cb) => {
      cb(null, {
        originalname: file.originalname,
      });
    },
    acl: 'public-read',
    contentType: function (req, file, cb) {
      cb(null, file.mimetype);
    },

    key: function (req, file, cb) {
      //generate unique file names for the server
      console.log(file);
      const uuid = uuidv4();
      const key = `${req.s3_key_prefix}${uuid}`;
      console.log(key);
      req.saved_files.push({
        originalname: file.originalname,
        mimetype: file.mimetype,
        encoding: file.encoding,
        key,
      });
      cb(null, key);
    },
  }),
});

const upload_auth = (req, res, next) => {
  //path to where the file will be uploaded
  try {
    req.s3_key_prefix = req.headers['x-path'].replace(/^\/+/g, '');
  } catch (e) {
    return next(Boom.badImplementation('x-path header incorrect'));
  }
  //all uploaded filesget pushed into this array
  //array is returned back to client once all uploads are completed
  req.saved_files = [];

  next();
};

router.post(
  '/upload',
  upload_auth,
  upload.array('files', 50),
  function (req, res) {
    console.log(req);
    res.json(req.saved_files);
  }
);

module.exports = router;

On the client-side, after the user presses the submit button, I do a post request with Axios.

const form_data = new FormData();
form_data.append('files', image);
const response = await axios.post(
  `http://localhost:8000/storage/upload`,
  form_data,
  {
    headers: {
      'Content-Type': 'multipart/form-data',
      'x-path': '/upload-folder/',
    },
    withCredentials: true,
  }
);

Sadly I run in the following error:

RangeError [ERR_HTTP_INVALID_STATUS_CODE]: Invalid status code: InvalidArgument: null
    at Request.extractError (/Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/services/s3.js:700:35)
    at Request.callListeners (/Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/sequential_executor.js:106:20)
    at Request.emit (/Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/sequential_executor.js:78:10)
    at Request.emit (/Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/request.js:688:14)
    at Request.transition (/Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/request.js:22:10)
    at AcceptorStateMachine.runTo (/Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/state_machine.js:14:12)
    at /Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/state_machine.js:26:10
    at Request.<anonymous> (/Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/request.js:38:9)
    at Request.<anonymous> (/Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/request.js:690:12)
    at Request.callListeners (/Users/sven/Documents/Devine/2020_2021/BAP/boilerplate/DURF_FINAL/server/node_modules/aws-sdk/lib/sequential_executor.js:116:18) {
  code: 'InvalidArgument',
  region: null,
  time: 2021-01-27T14:49:26.441Z,
  requestId: 'tx00000000000000816654e-0060117d77-279bd-ams3c',
  extendedRequestId: undefined,
  cfId: undefined,
  statusCode: 400,
  retryable: false,
  retryDelay: 87.53896917819553,
  storageErrors: []
}

Does anyone know what is going wrong?