loadFromJSON ignores custom properties after loading Fabric JS

I am working with 1.5 version and I get some weird issue. I get JSON and my custom properties are exported and saved in my server side

canvas.includeDefaultValues = false;
var json = canvas.toJSON(['centeredRotation', 'selectable']);
return JSON.stringify(json);

But after load the canvas JSON the custom properties disappear I don't know why I load the json as following:

function loadCanvasFromJson(canvasM) {
    var jsonCanvas = $('#jsonCanvas').val();
    var jsonObject = JSON.parse(jsonCanvas);
    jsonCanvas = JSON.stringify(jsonObject);
    canvasM.loadFromJSON(jsonCanvas, canvasM.renderAll.bind(canvasM));

    setTimeout(function () {
        var objects = canvas.getObjects();
        console.log(objects);
        for (var i in objects) {

            var positions = calcPixelsByPercentage(objects[i].percentage_left, objects[i].percentage_top, canvas);//percentages positions
            var size = calcPixelsByPercentage(objects[i].percentage_width, objects[i].percentage_height, canvasM); //percentages size
            /*calculating new scale objects responsive*/
            var scale = size.left / objects[i].width;
            objects[i].scaleX = scale;
            objects[i].scaleY = scale;
            objects[i].left = positions.left;
            objects[i].top = positions.top;
            objects[i].setCoords();
        }
        canvasM.renderAll();
        console.log('after load Canvas');
        console.log(canvasM.toJSON(['centeredRotation', 'selectable']));

    }, 1000);
}

thanks for your help I guess there is a bug somewhere.