I'm sorry to hear that! Its hard to get motivated when you're feeling bad .I don't think its going under the apron,probably the door or roof. They climb good.We had a problem with big rat snakes getting inside our young pea fowl pen years ago.They'll kill adult chickens if they're hungry
There are no gaps at the roof.
I don't have the coop article done, but this is the build thread: https://www.backyardchickens.com/threads/large-open-air-coop-in-central-nc.1443812/
I should be able to do the inspection today.