Bug in imports.ui.tweener?

[Juan Simón <decedion gmail com>]

I have asked for help in previous messages by a problem with tweener.

I have defined the next class in my extension:
-----------------------------------------------------------------------
const IconAnimated = new Lang.Class({
    Name: 'IconAnimated',
    Extends: St.Icon,

    _init: function(icon_name, style_class) {
       
        this.parent({ icon_name: icon_name, style_class: style_class });

        this.TweenIn = {
            opacity:50,
            time:1,
            transition:'easeOutQuad',
            onComplete: function() {
                Tweener.addTween(this, this.TweenOut);
            }
        }

        this.TweenOut = {
            opacity:255,
            time:1,
            transition:'easeOutQuad',
            onComplete: function() {
                Tweener.addTween(this, this.TweenIn);
            }
        }

    },

    startAnimation: function() {
        this.set_icon_name(ICON_ACTIVO);
        Tweener.addTween(this, this.TweenOut);
    },

    stopAnimation: function() {
        Tweener.removeTweens(this);
        this.opacity = 255;
        this.set_icon_name(ICON_INACTIVO);
    }

});
-----------------------------------------------------------------------

This animation could be repeated for several hours, depending on the duration of the process monitored by my extension. But after 8-10 minutes the animation stopped. I tried several possible solutions but none of them work. Finally I changed the import from "imports.ui.tweener" to "imports.tweener.tweener" and now it works well. Is this a bug of "imports.ui.tweener" or a wanted functionality?