The briefing module is bugged. What I mean by that is that when we click on "OK" (so when we are done with the briefing), the module disappears. I don't know if the players can see it, but it disappears on Zeus' interface. Also, when clicking on "Cancel", the briefing module will stay on the map, but without any description (empty).
I uploaded a private video, to illustrate this issue:
https://www.youtube.com/watch?v=JW6wK0aasUI&feature=youtu.be