During an attack ( raider, roach, mole, or deathclaw ) your dwellers begin to panic and do the Dweller Shuffle. The dwellers leave their work positions and scramble around the room, randomly standing still to fight. Before the update this was just a nuisance, but now the monsters are all stronger , even the previously weak radroach Is capable of killing dwellers if not attended to. The result is your dwellers doing the Dweller Shuffle and randomly stopping on top of each other and trading places. If you are anything like me, then you keep all dwellers in a room in the same outfit. So your left chasing dwellers around the room and trying to click a wounded dweller behind a healed dweller. While your fighting to heal one dancing dweller, the rest have tragically passed on. If you have not used all your stimpacks yet, and your room is dead, the conjoined rooms are then affected the same , but now there are more to chase around with less stimpacks to spare. To make these matters worse, these attackers are killing workers in production rooms haunting production and draining resourses , so if your low on caps you end up with all your dwellers dead and no power water or food. And not even a dweller to work the rooms to make caps to revive other dwellers. In the end. The update has killed the game.

Can I stop update? Mine is Android version, I hope it is not too late...

If you have already updated it is too late, unless you back up your device on a computer. Then delete the updated app and re download it from the computers backup,

My game version currently is 1.1.320, is it too late?

for iOS the bad update is the 1.1 update.