I think you might misunderstand what the problem is or I didnt write it clear enough
I know that DOM elements are rendered on top of non DOM elements, which is fine as its not the problem, so its not important.
The issue is if you click and hold down the mouse button on a progressbar as if you wanted to drag it somewhere. (As I wrote in the initial report, this obviously wont work as it doesn't have dragdrop behaviour). But regardless of that, after you have done it, other objects like the sprites which actually have dragdrop behaviour will no longer work. The mere fact that you simply "simulate" a dragdrop with the mouse on a progressbar will make it ruin the dragdrop behaviour for other objects.
So simply, make a progressbar or a few and scale them down a bit as it doesnt seem to happen everytime and with every progressbar, after that make some sprites which have dragdrop behaviour. When you run the app. first try to dragdrop the sprites, this should work fine. Then try to dragdrop the progressbar and after that try to dragdrop the sprites again and see if they still work.