I’ve been experiencing this issue on both PC and Xbox One. This issue makes a lot of the conversations hard to follow as your character is often speaking to someone that’s behind you. This also affects other conversations between NPCs.
Support.gearsofwar.com please submit a ticket
You need to click which game first.
Edit: I apologise, the option currently seems to be missing
Here is the link https://support.gearsofwar.com/hc/en-us/requests/new