Get project custom fields (Project Server)

I am trying to access, in a project detail page, the project context via Javascript to retrieve the data of the custom fields.

But my problem is that, when I try to access all the data it only shows me three fields, and there are at least 20.

My code:

<script type="text/javascript">

var contexto;
var proyecto;   
var fields; 


    function init() {       

        contexto = PS.ProjectContext.get_current();
        proyecto = contexto.get_projects().getByGuid(PDP_projUid);
        fields = proyecto.get_customFields(); 
        contexto.load(fields);
        contexto.executeQueryAsync(Function.createDelegate(this, this.Exito), Function.createDelegate(this, this.Error));

    }

    init(); 

    function Exito() {

        console.log('Exito');

        console.log(fields);
        console.log(fields.get_count()); 

        for(i = 0; i < fields.get_count(); i++) 
        {
            console.log(fields.get_item(i));            
            console.log(fields.get_item(i).get_name());
            console.log(fields.get_item(i).get_description());
        }

    }

    function Error() {
        alert('Error'); 
    }

</script>

All the fields, are controlled by the workflow, even the three that are successfully shown.

Any idea why this happens?