In a nutshell: Make very agent a bit different in the sense that they all won't make the exact same choices. i.e. Rather than have a human always choose the first source, vary this and have some humans that go for the fifth and others for the sixth, etc. etc. Your random selection would also work I guess. Although how well? I don't know.

Then, have a global pattern of how everything should be working, more or less. When a major deviation is found from the global pattern, adjust. How exactly? Those are implementation details.