My game has never crashed, failed or appeared Buggy in the slightest. Im running it on an Ipad Air.
iPad 3, playing two vault games, no crashes, only the code bugs everyone else has. It's not everyone, and thankfully, it's not me!
I'm on a 5s and haven't experienced any of the reported crashes or bugs. Interesting.
5s and also did not experienced any bugs. Minor ones like unable to relocate a dweller was able to be fixed by restarting game and phone.
Also 5s here and no issues whatsoever. I can't say the same for my iPad mini, though.
Running on 5s. Game crashes occasionally. Suffering from pregnancy bug, lagging wasteland explorers menu. You name it.
iPad Air 2 - 117 Dwellers, no lags, no crashes, no bugs.
iPhone 6 - 41 Dwellers, no lags, no crashes, no bugs.
If some players with same devices like iPhone5s have no problems, and others have - that means, your settings or other programs affecting this game.
Or it means these people have lower expectations or they aren't playing this game as often or they haven't progressed as far as others.
Fallout Shelter is supported for the iPhone 5 and up, the iPad 3 and up, and the iPad Mini 2 and up. It is optimized for the iPhone 6, 6+, and iPad Air 2. The game runs on iOS 7 and up.
If you have the systems that should be up to snuff, you might want to try a few things, including resetting your device and closing other applications.