var node = this.vis.selectAll(".node").data(nodes, function(d) {
                    return d.id;
                });

  var svg = node.enter().append("svg:svg").classed("node",true);
        svg.append("svg:image").attr("href",function(d){return d.src});
        

as above, when you click Refresh, the nodes data has been updated, but the data obtained by d on img is still the data previously bound, not the latest data