Can't change Text Properties from scripting

Hi Everyone,

I made a script to change all the fonts in a project, but since some days, nothing works anymore.

Is there a nex feature in AE 17 ?

Here is a simplified code with the fontSize;

var myComp = app.project.activeItem;

var myLayer = myComp.selectedLayers;

myText = myLayer[0].property("Source Text").value;

alert(myText.fontSize);

myText.fontSize = 60;

The alert returns the actual font Size, but nothing changes. It's the same with all other properties font, tracking, justification...