I'm not sure what's causing it, but I'm experiencing population loss at 0 heat. It's like heat isn't actually being updated when it should go down? Going to see if this persists on reload / import. If so, I'll add a comment here with the save.
Hey there, thanks for playing! A base heat and therefore population loss is currently intended but we already see that this is not intuitive for some players. We will work on improving that :)