This is probably because of this 'fix' in Mx 7.12
So it probably now also includes other css files in the ui folder, such as these css files in the ui/flat folder for example, that's probably why it shows one with and one without the full url, because the css in the ui/flat folder do not have the full url.
Haven't tested this theory yet though :)
But if this is indeed the case, the fix would be to remove these css files, as there not really used by the widget (as far as I can see), but your best bet is probably to create an issue on GitHub and ask for the widget to be made 7.12 compatible
Edit Just tested it, and confirmed my theory. Removing the additional css files in the ui and its subfolders, fixes it