This just happened yesterday at my server.
I was minding my own business doing things at my server, and I had to duplicate something. So I duplicated it and it said: "5/5 duplicated succesfully." on my screen. But when I duplicated it AGAIN no bricks were planted, it just said: "5/5 duplicated succesfully." . I had to have thought one of my supers messed with the prefs. But when I checked it was all the same as to when I set it. I don't know what's going on. But should I re-download or is it some bug that can be fixed? Please help.