You'll need to ask for more direct support of Fadmin, or how to remove it, to not conflict with any script expecting superadmin to be highest, at the DarkRP forums or Wiki.
Also, from now on, I'm moving every 'DarkRP breaks admin groups I set using ULX' to Off-topic.
The same question has been asked many times before. It's not ULX breaking, it's DarkRP or conflicting addon changing groups.