Hey everyone! Haven't found a workaround/fix for the issue yet, but /u/gransom over on www.reddit.com/r/foshelter/ may have found the objective causing the crash. He dug into his save and mine and found an "Equip Missile Launcher" objective on each. Unfortunately, I don't have a launcher yet and he has a few days until he can get one of his dwellers back w/ a missile launcher to see if equipping/unequipping will fix the issue. If anyone here has a launcher, give it a shot. Or if you can post your save file for gransom over on reddit, it might help confirm which objective is causing the problem. Here's a link to his post:
https://www.reddit.com/r/foshelter/comments/3ibmnt/objectives_crashing_and_possible_cause/