Just started playing this game yesterday on my iPad mini.
Early in the game when you have a small amount of dwellers, the game seems to operate fine. Once I get past 20 dwellers the game becomes unstable and starts to crash more frequently. Once I get up to around 24 dwellers, I can't open that vault anymore.
Once that happened, I wondered if the vault became corrupt somehow. So I created a new vault and the same thing happened again. The less dwellers, the more stable the game. Once I get past 20 dwellers the game crashes constantly. When I get to around 25 dwellers, I can no longer play the vault. It just crashes when you try to open it.
I'm really bummed as I enjoyed the game. I also purchased $25 in vault lunch boxes between my two vaults. If I can't play the game, I wouldn't mind getting a refund.
I'd prefer a fix.