Love your plugin!! :)
On Firefox the icon isn't visible after its moved over to the circle (probably a z-index issue?). After further testing, whenever I load any post and try to click on/move an icon it disappears completely. I can make them all disappear (usually they move back to a spot in the list).
On Safari, it works but if you make a mistake and then click the back button the icons are not moveable. If you reload the page/post then everything is fine.
We have a few other plugins installed but none that are captcha-related.
You can test here:
Hoping you can sort this out :)