Error: RNFetchBlob request error: Value for head cannot be cast from ReadableNativeMap to Stringnull

I've just started receiving this error, my function always worked fine previously and I'm not sure what changed with RNFetchBlob.

Can anyone explain why this might be?

const _path = this.getPath(path);
    const _data = JSON.stringify(data);
    const _headers = {
      ...this.service.defaults.headers,
      Accept: 'application/json',
      'Content-Type': 'application/json',
    };

    RNFetchBlob.fetch('POST', _path, _headers, _data).then((response) => {
      const filepath = `${RNFetchBlob.fs.dirs.DocumentDir}/invoice_${data.code}.pdf`;

      // Write file
      RNFetchBlob.fs.writeFile(filepath, response.data, 'base64');

      // Open file
      if (isIOS) {
        RNFetchBlob.ios.previewDocument(filepath);
      } else {
        RNFetchBlob.android.actionViewIntent(filepath, 'application/pdf');
      }
    });

joltup / rn-fetch-blob

Error: RNFetchBlob request error: Value for head cannot be cast from ReadableNativeMap to Stringnull #747