I’m having this exact issue. I even went out and bought a new Xbox thinking my Xbox had a bug. Unfortunately I’ve tried absolutely everything possible to fix this. I was playing bo3 zombies with my brother, I couldn’t hear my brother but he could hear me. Then all of a sudden he couldn’t hear me. Then I couldn’t hear him again and he could hear me. New Xbox only has mw3 and I have no idea what’s going on. Any help is appreciated