Game "lags" when are hostile mobs nearby / Too many mobs

I am tracking this bug since i started to play mcpe (0.7.2 version) and is not solved either in 0.7.6!.When is night and hostile mobs appear if i try to move arround screen the game "lags".I am sure that the mobs are the cause (skeleton,creeper,zombie,spider) ,beacuse if i change the game difficulty to easy (no mobs) the game run normally.I am playing on a Samsung Galaxy Ace 2 device with Android 2.3.6 Gingerbread.Thanks