PC Dialogue only through centre speaker when using 5.1 surround

On PC when using the 5.1 surround option, the dialogue and the effects on the same channel only come out of the centre speaker, even at times where they should come out of one of the other speakers. The music, normal sound effects, and even background character dialogue comes through the correct speaker according to position.

The quality of the sound through that speaker is also reduced causing the scene taking place to feel jarring with the lower quality sound and misplaced positioning.

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I have tried repairing the game and checked my own surround audio settings, the audio in other games and movies is fine.
I would very much like a solution so that I can enjoy the game at it's fullest.