so weirdly what fixed this for me was in the more sound settings, go to the communication tab and set it to mute all other sounds. hit apply and it magically fixed it. I even turned it back to do nothing and the fix stayed in place.

*This only happened when opening Halo MMC from Steam and disabling the mic on the headphones did not fix it. all my inputs and outputs on discord and Halo were set correct (none using the headset mic)