With the iOS simulator version 10, double clicking the home button to bring up multitasking (running apps) sometimes does not respond. Even hitting (cmd + shift + h)x2 to simulate home button double click also works sometimes. I have verified this with a work mate and they have the same issue. I am not sure if this is a bug in the simulator or if there is a setting somewhere on for example the delay between the clicks? The answer from here did not make a difference.