Why my home button doesn't responding when I double tapping it?

[iMore Question]

I am using an ipod gen5. I just installed the new software iOS 8.1.1 . Before installing, my home button-double tap was functioning very well but after installing, my home button-double tap is not functioning. Why does this happen ? I cannot kill apps at all!

 

[Speedygi]

The button's mechanisms could be loose or just plain unresponsive, get it repaired.