it's probably a bug. i've seen some problems with the latest update not triggering the load complete event in as3, too.
you can check if the bug you've noticed has been logged: https://bugbase.adobe.com/
I've noticed that too.
One friend reported that his portfolio website doesn't work anymore. Its one main.swf file which loads gallery.swf file which holds photos.
It was working fine for me, than I realised that my flash player is 11.5, after I upgraded it into latest 11.6 it stopped working.
Website is full screen swf. When gallery (button click) load attempt is made, instead of loaded gallery, blank screen is shown.
Right click shows: "Movie not loaded" message
gallery.swf is loaded with this command: loadMovie("gallery.swf", "GalleryHolder");
It's 3 years old AS2 project.
It's not big deal for me because Ill re-make it with jquerry gallery, and flash is generally being hated anyway.
Im not happy about bad hype against flash but we need to move on.
But it could make big problems for other people because their projects will stop working.