It's because those islands are missing an 'anim' folder. An 'anim' folder basically contains a mission.sqm, and an intro script that loops.
Most islands come with an 'anim' folder that you just put in the addons folder, but some do not. You could try making your own anims for that island. You just gotta make sure that the camera script you use loops continuously.
Hope this helps
Gruntage