It works perfectly well, all the times, every time with every site.
Problem, it doesn't show the site favicon.icon on the Desktop, it shows Firefox boring url shortcut icon on all of its desktop shortcuts, so if you have 25 URL shortcuts on your desktop and everyday you delete and add few here and there, you can see it becomes very problematic. You can't figure out which shortcut belongs to which site without highlighting it or clicking on it or activating it, a total waste of time.
P.S. The older DeskCut has same problem, it doesn't preserve the site favicon, only SaveLink works to perfection but alas not compatible with Firefox Quantum.