So far I have only test the iFrame. You can also see it in the example you provided if you change the full screen mode to stretch, then drag the size of the window around... the buttons as well as the frame "slide" out of position.
If you can eliminate this bug, it would be super cool since I am working on a website now in HTML5 using C2. The deadline is soon, and your iFrame saved my ass basically. This bug is holding it back however, and I would love to use this in the final product!
I appreciate the time you have spent on this, and any future updates. Awesome plugin mate :D