Yes, I agree that hardy chickens can also hibernate outside if you’re climate isn’t too harsh.
Maybe it's an idea to just let them choose where they want to sleep? chickens will actually go to sleep indoors if they prefer it there. Some things they can figure out for themselves.
As long as...
Well you never know with chickens.
Originally I had only 4 tiny chickens in a prefab coop. I rebuild it and added an airy extension to this coop: a sheltered place with roosts to hang out during the day. It is attached to the small coop/run, which was rather small. They preferred to sleep in...
If you grab them at dusk when they are roosted its quit easy to pick them up.
What I did to get the chickens in the run around sunset after free ranging: scatter a few hands of treats (eg. grains/corn mix or a few mealworms ) in there. Its really a good trick to get them where I want them to...
Maybe it helps if you bring more daylight in the coop. Some birds don’t like to go in a coop that’s dark.
Another reason could be parasites. Did you check on mites?
But it also might be a habit. It can take several weeks to break a habit you don’t like. I had chickens who liked to stay outside...