Dialog won't close in AFX CC

I have updated my After Effects from CS6 to CC (13.0.2.3). I'm still trying to figure out why some of my scripts won't run anymore or why they make CC crash sometimes.

Now, when one UI dialog calls another UI dialog, after a few clicks both of them will not close any more, neither by code (myDialog.close() returns undefined)  nor by clicking on the Close button of the dialog title bar.

How come it worked in CS6 but now in CC it works for a few clicks only and then stops? What am I missing?

Here's the stupid piece of code I wrote to test this:

//DIALOG 1

var dlg1 = new Window('palette', 'Dialog1', undefined);

var btn1 = dlg1.add('button', undefined,'Call Dialog2');

//Calls Dialog 2

btn1.onClick = function()

{

    dlg1.close();

    dlg2.show();

}

//DIALOG 2

var dlg2 = new Window ('palette', 'Dialog2', undefined);

var btn2 = dlg2.add('button', undefined,'Dialog1 Call');

//Calls Dialog 1

btn2.onClick = function()

{

    dlg2.close();

    dlg1.show();

}

dlg1.show();