When a hive has a problem, bees will come up with creative alternatives to stay in the hive.
In this case, Gertrude hive had winter boarders in the hive first floor so bees used a crack in the back to get into the hive. The mouse family destroyed about half the frames and were too big for the bees to chase out.
After removing the damage the mice did, I had to close the hive top for a few weeks to encourage bees to use the front door again.
It's not so bad in early spring when hive numbers are low. By end of July, though, there can be as many as 80,000 bees in one hive and they will need a much bigger door, and home, to get in and out!