I am not the fastest player of this game which tends to show up when dealing with the bomb screens...

I am not the fastest player of this game which tends to show up when dealing with the bomb screens. However it has happened that several times my poor birds have been blown up not because I was too slow to act, but because the birds tend to freeze on their branches and fail to fly. It needs several tries by which time the bomb has gone off. I used to think it was due to frantic efforts to speed up, making my movements clumsy, but it is more than that- the birds can freeze even during quiet parts of the game. Why is this?