We are making use of the latest Docker image located here
I'm unsure of the specific version it uses
Edit: Your response made me realize that if you build your images with every push to your repo that could be the problem - that and the fact the latest push was only 3 hours ago.
I changed the docker image to nodebb/docker:latest-v1.10.x and that fixed it. Honestly, this is something I should have spotted myself without having to be prompted. Thanks @baris