I've had that situation before. Check immediately after dusk to make sure everyone is in and settled down/settling down. It takes a few days or a week to sort out the perch hierarchy. Robin likes my big roo Goliath, he doesn't block the door but he plops down in front of it. The chicks still get in.I moved the chicks into the coop, they seem to be ok just being on the perch now but I'll leave the box in for another day to see if they still want it. However, all of the big girls are on the other perch and both groups clearly prefer to be kept separate, with the small ones afraid to go up the ramp at night due to the big birds being next to it going up themselves.