I'm not 100% sure if this counts as a bug, but it is certainly annoying. If you choose Carthage as your Civ, they can walk over mountains, however they lose 50 health each time they rest on said mountains. Well, if you set workers to automate their improvements, they seem to not know any better and die ALL THE TIME from Attrition. Basically, they rest on mountains continuously and kill themselves. It was super obnoxious last game I played, so it'd be nice if it was changed.