Same for me, the save becomes corrupted (it's not the device since this happens on two of my devices with the same "Vault" save file - Galaxy S4 and Nexus 6)
Cannot really play the game at present as I am only challenge chasing for lunchboxes.
There is a support thread for the same issue here:
http://www.gamesas.com/topic/1532994-objectives-crash-my-game/
Note that someone posted a link to my fix on that thread, which a number of people has found helpful.
Been having this problem on my iPhone 5S 16gb for a couple of days now which makes it really difficult the play the game.
As soon as I click the Objectives button (little ribbon icon) the game freezes and completely crashes. I cannot even see what objectives I've currently got. I really want to chase the objectives and it makes the game really boring now as I cannot do much but keep maxing my resources and leveling characters stats/level.