Halo 4 Final Mission Bug Report

Hi, I have a problem when I was playing the Final Mission. When we were going to plant a grenade on Didact, the game told me " Use RT to Fire the Machine Gun", but I have never made it. After searching the video, I saw “Use LT to Plant Grenade”, then I tried and made it. I think it probably is a translating bug. My game language is Traditional Chinese, and I hope it will be fixed. Thanks!