SI Outbound Gateway - desempacotando a resposta de volta para a classe JAXB

Boa tarde,

Estou usando um gateway de saída para chamar um serviço que pode consumir XML (não SOAP) e produzir XML (não SOAP). Posso empacotar a classe JAXB para solicitar XML, mas não consigo descompactar a resposta XML de volta para as classes JAXB, o corpo da carga útil é nulo.

O fluxo é o seguinte

                            .subFlowMapping("SomeRequestType", subflow -> subflow
                                    .transform(someRequestTransformer)
                                    .enrichHeaders(header -> header.header("Content-Type","application/xml"))
                                    .handle(someServiceOutboundGateway)
                                    .transform(someResponseTransformer)
                            )

DesomeServiceOutboundGateway

@Bean
public HttpMessageConverter m() {
    MarshallingHttpMessageConverter c = new MarshallingHttpMessageConverter();
    c.setMarshaller(someMarshaller());
    c.setUnmarshaller(someUnMarshaller());
    return c;
}

@Bean(name="someServiceOutboundGateway")
public MessageHandler someOutboundGateway() {
    return Http.outboundGateway(someUrl, lnquiHttp())
            .httpMethod(HttpMethod.POST)
            .expectedResponseType(Response.class)
            .get();
}

@Bean
public RestTemplate lnquiHttp() {
    PoolingHttpClientConnectionManager connectionManager = new PoolingHttpClientConnectionManager();
    connectionManager.setMaxTotal(connections);
    connectionManager.setDefaultMaxPerRoute(maxConnectionsPerRoute);

    RequestConfig requestConfig = RequestConfig
            .custom()
            .setConnectionRequestTimeout(timeout) // timeout to get connection from pool
            .setSocketTimeout(timeout) // standard connection timeout
            .setConnectTimeout(timeout) // standard connection timeout
            .build();

    HttpClient httpClient = HttpClientBuilder.create()
            .setConnectionManager(connectionManager)
            .setDefaultRequestConfig(requestConfig).build();

    ClientHttpRequestFactory requestFactory = new HttpComponentsClientHttpRequestFactory(httpClient);

    RestTemplateBuilder restTemplateBuilder = new RestTemplateBuilder();
    RestTemplate restTemplate = restTemplateBuilder
            .requestFactory(requestFactory)
            .basicAuthorization(userName, password)
            .messageConverters(m())
            .build();

    return restTemplate;
}

@Bean
public Marshaller someMarshaller() {
    final Jaxb2Marshaller marshaller = new Jaxb2Marshaller();
    marshaller.setContextPath(CONTEXTPATH_REQUEST);
    marshaller.setSchema(responseSchema);
    marshaller.setSupportJaxbElementClass(Boolean.TRUE);
    return  marshaller;
}

@Bean
public Unmarshaller someUnMarshaller() {
    final Jaxb2Marshaller unmarshaller = new Jaxb2Marshaller();
    unmarshaller.setContextPath(CONTEXTPATH_RESPONSE);
    unmarshaller.setSchema(responseSchema);
    unmarshaller.setSupportJaxbElementClass(Boolean.TRUE);
    return  unmarshaller;
}

@Bean(name = "someJAXBContext")
public JAXBContext someJAXBContext() throws JAXBException {
    return JAXBContext.newInstance(Response.class);
}

desomeResponseTransformer

@Component
public class SomeResponseTransformer implements GenericHandler<Object> {

    @Override
    public Object handle(final Object payload, final Map<String, Object> headers) {
        ResponseEntity responseEntity = (ResponseEntity)payload;
        Object body = responseEntity.getBody();
        Response lnqiResponse = (Response)body;
        ... = buildHeader(lnqiResponse.getHeader());

Quando estou tentando obter o cabeçalho ( lnqiResponse.getHeader()), recebo um NullPointerException.

Alguma ideia, por favor, de como descompactar a resposta para o Response? Qualquer ajuda seria apreciada! Obrigado!