I had a similar ‘problem’ with all my youngsters in the passed years.A new mystery: all three older pullets are dozing on a roost outside the coop. (They’re inside a fully protected and locked run; just not inside the Nestera coop.) They’ve been there for a hour and a half. This after they routinely stand in the open doorway at dusk, calling a straggler to come in and join them.
A few hens don’t tolerate juveniles to roost with them in the extension where all my chickens used to sleep.
My run is not very safe and open (netting on top).
I added an extra coop last year hoping to solve the roost problem. The mother (Ini mini) and her big ‘chicks’ went to the new playhouse when their brooder-coop became too small.
Now my chickens are divided over 2 coops and there are all safe at night and I have no problems around roost time anymore.