Balrog glitch???

I love this game, but I cannot defeat the Balrog at the end of The Bridge of Khazad-Dum, where Gandalf is on top of the Balrog and they are falling. I have tried many ways of tapping and have come to the conclusion that it is a glitch in the game. Half the time the game does not even register that I tapped so the time runs out and the purple bar fills up again. If this is broken, please fix it! I want to finish this game!

Shadowfax The Mearas about LEGO® The Lord of the Rings™