Kia ora
I have a simalr issues but, I use a compiolit ( device that hangs round my neck that talks via bluetooth to my hearing aids) this has a jack pug that plugs into the headphone socket, if I use this I get echoing very low voice dialog and normal sound, if I use my speakersas normal the dialog is ok. I tried to set the audio from 5.1 to headphones and no change, seems the audio channels in this game are limited and it's not transfering to the right places. I get the felling it's the fact we use headphones thats broken, it cant play 5.1 to headphone correctly