And just as I think I figured out what the problem was. I noticed digging through the rules that you gave every faction its own settler unit and made the default Settler and Engineer (Wizard and Necromant) civ-specific. I loaded up test.sav from this post, removed the 'Not _x' from all civs' tech, and lo and behold the suicide stopped. My guess is blocking access to the default settler units confused the AI; I don't think I've ever seen a scenario block them outright without pre-placed cities. You're not using a rich text editor, are you? I've written events out by hand in Notepad and as long as it's all proper format and syntax it works fine.