Yes because you dont have enough housing. people need free living space to migrate.
That is the problem. You will never get enough houses. When you get enough, they breed and you start lacking houses again. In late game you can't have enough houses. Why an homeless and jobless colonist cannot move to a dome without houses and jobs? At least the specialist would move to domes where they can take jobs when people retire.
When you have homeless problem sanatorium start to become empty and the number of flaw they should treat increase. All is broker as soon as you get homeless people. Just becasue you can't do anything (moral) again endless breeding. And also because of the rules don't move if no house even if you don't have house where you are.