Ajax load in cakephp 3.4+

I am trying to load a form to add a record using jquery.load()
Here is my code :
$("#edition-div").load(“forum/threads/add/” + id, function(response, status, xhr) {
if (status == “error”) {
var msg = “Error: “;
$( “#edition-div” ).html( msg + xhr.status + " " + xhr.statusText );
} else {
$(‘html, body’).animate({scrollTop: $("#edition-div").offset().top}, 1000);

This works perfectly in 2.6 and 2.8 (and before) but not in 3.x.
There is no javascript error and no php error.
The div (edition-div) loads the current page.
The template (threads/add) is not loaded.
The ajax layout is not loaded either.
The add method in the controller is the standard baked add function.