If an application has errors (such as a Deployment with 0 activations) and you try to update the application's configuration (e.g. to set keep-deployments), the broker will fail with an error.

On https://github.com/openshift/origin-server/blob/master/controller/app/models/application.rb#L408, self.errors.messages doesn't contain a key called :config. In my example, it contains :deployments=>["is invalid"].