After beating the main quest (Was also the first time I used a city plan), sometimes various settlement values change to an extremely high number (starts with 429) and happiness decreases, it fixes itself once I go to that settlement and open the workshop, it's still really bad, if you don't notice it. Especially since you can now lose settlements if their happiness is too low, and I don't want that. After all it said I'll need a lotta settlements in the next part.