It was stable, now it's crashy. Think it's Lemonjelly's Worker Mod, sadly. None of the CtDs are repeatable but it's just too annoying to keep the mod.
EDIT: Hmmm. Or Scions Healthcare. Let's try that.
Probably this has been noted, but if you build a city on top of a Fort Commander you keep the Commander forever. Found this out by accident - forgot to delete a civ, so the map was supercrowded and I had this narrow fertile band above the ubiquitous Giant Desert Area of ErebusContinent, so I was forting future city sites to keep the AI out (I managed to fort exactly one that they didn't just city the edge of).
Anyway, I settled on top of a fort, and the commander remained to hang out as a 52xp city guardian. I was Mechanos, next turn I turned him into a Mobile Fortress....