I'm not sure of the situation myself cause the command blocks don't give any clues as to what's up. Please just look into it, it makes the Star Wars Mash-Up Pack unplayable as you need the ships to get around the different areas in Survival.
Why is it RESOLVED, nothing's been done about it and it's still broken!
Ive had a similar problem where I start up a world, then after a good few minutes have past (around 15 minutes I counted) when I exited and saved the world, I would just be stuck on a "saving world" screen that doesn't finish, forcing me to quit the game. When I load up the game again, the world isn't there anymore. And I have autosave on, so this should not happen.