Download with primefaces 5.3 after 5.1 migration does not work

I'm migrating from primeface 5.1 to 5.3. It was meant to be simple, just change the version in maven.

But it's not quite right

The p: fileDownload command no longer works

<p:commandButton id="exportarArquivo" icon="ui-icon-print" value="Exportar arquivo" disabled="#{comissaoCobradorMB.isParametros()}" process="@this" > 
    <p:fileDownload value="#{comissaoCobradorMB.file}" />
</p:commandButton>

Debugging the following error appears in browse (chrome).

Request return with error: parsererror. primefaces.js.xhrml: 1

Below MB

The code is a bit old but it worked.

Note that a report is generated. I checked and the same is generated.

public StreamedContent getFile() {
        geraRelatorio();
        return this.file;
    }


    private void geraRelatorio() {
        String path ;
        String nome ;
        String extensao;
        String pathReal ;
        String pathNome ;

        DateTimeFormatter fDataParaString = DateTimeFormatter.ofPattern("yyyyMMdd");
        DateTimeFormatter fDataParaStringData = DateTimeFormatter.ofPattern("dd/MM/yyyy");

        Map parametros = new LinkedHashMap();
        parametros.put("Data De" , fDataParaStringData.format(getDataInicial()));       //fDataParaString.format(this.getDataDe()) ) ;  
        parametros.put("Data Ate", fDataParaStringData.format(getDataFinal()));         // fDataParaString.format(this.getDataDe()) );

        extensao = "."+this.getTipoArquivo();
        path = "/WEB-INF/temporarios";
        nome = "comissaoCob";
        nome+="_De_"+fDataParaString.format(this.getDataInicial());
        nome+="_Ate_"+fDataParaString.format(this.getDataFinal());
        nome+="_Gr_";

        FacesContext facesContext = FacesContext.getCurrentInstance();  
        ServletContext servletContext = (ServletContext)facesContext.getExternalContext().getContext();
        pathReal  = servletContext.getRealPath(path);

        nome = Texto.nomePadrao(pathReal, nome, extensao);

        GeraArquivoTipo geraArquivoTipo;
        if(this.getTipoArquivo().trim().equals("PDF")){
            System.out.println(".............Entrou no PDF");
            geraArquivoTipo = GeraArquivoTipo.PDF;
        } else {
            geraArquivoTipo = GeraArquivoTipo.EXCEL;
            System.out.println(".............Entrou no Excel");
        }

        new RelatorioDeComissaoDeCobradores(comissao,pathReal.trim()+"/"+nome, parametros, geraArquivoTipo);

        pathNome = path+"/"+nome;
        InputStream stream = servletContext.getResourceAsStream(pathNome);            //getResourceAsStream(path+nome);
        //this.file = new DefaultStreamedContent(stream, "application/octet-stream", nome);
        this.file = new DefaultStreamedContent(stream,"application/pdf", nome);


    }