Refusing to Coop at night - Missionary in Africa needs help

I am vice president of a non-profit corp. that provides financial and logistical support for missionaries in Sierra Leone, West Africa. Today, I received the following from Laura Holt and am hoping that folks here can offer some guidance. They have quite a bit of experience raising chickens in America, but being in Africa changes the whole game. This is one of several chicken problems they need help with, but I am splitting it up so that it goes to the appropriate forum section. The complete letter and a couple of photos are posted here - http://www.southernagrarian.com/chickens-in-africa/
Notes in [brackets] are mine.

Problem One: they utterly refuse to go into the coop at night. Initially Mercy [their Australian Shepherd] and I were herding them in. He is extremely good at it and we managed to force them in with relatively little trouble. Slowly but noticeably they became more difficult to persuade to go inside. We tried a light; a leg off the PV [solar power] system. No way. For the last week I have given up and allow them to sleep outside. They are so content and my reluctance to force them in is that when they are in the coop they bunch up so badly that I regularly had suffocations. They tightly pack just inside the door as if to say, “Alright, you want us in but we will go no further.” There is plenty of room. They are not afraid of the coop; they go in and out all day; that is where the laying boxes are. I am just stymied by the behavior. When outside they loosely group together for the night but not in heaps like when inside. We are considering closing in the feeding shed, which is open on two sides, with gates that can be opened during the day to allow ranging in the yard and closed at night.(see picture at the bottom) The trouble with letting them just be out in the open at night is animals and particularly cobras whom we are told have a fondness for chicken. Suggestions?

[If you think you have predator problems where you are, "you ain't seen nothin"]