@Semaphorism: The problem here is Spacebook. You can fix it by running the following console command:
"/c game.forces.guests.set_friend('miniloader', true) game.forces.miniloader.set_friend('guests', true)"
Repeat for any other teams/forces you may have in your game. Using the Spacebook GUI isn't enough, because it only keeps two teams from shooting each other ("cease fire"), but doesn't give access to chests.
Spacebook does interesting things with teams / forces, which Miniloader doesn't handle. I'll work on a fix for this.