I have no idea.. have you tried clearing the garrysmod\cache\dua folder? You mentioned something about 'updating' it, maybe try removing the folder completely and let the server rebuild it?
I will try this and update this post on how it turns out.
Usually, I just drag the 'dua' folder onto my desktop and then drag it onto my FastDL server. I had assumed that the whole entire cache gets updated every map change since it says the files were modified around the same time the map changes.
Edit ----
Unfortunately, this did not work. It's still making me redownload some lua files and whatever is downloaded is getting blocked.
Edit 2 ---
Also, I'd like to make a request to go back to the basics of my first post. It's been 2 weeks since I made this thread and the progress of it has been slow. I appreciate all the help, but I think it would be quicker if the original ULib and ULX be recoded to fix the ban mechanics rather than introducing me to XGUI.