I'm not sure if this is necessarily a bug or not, but it makes gameplay awkward nonetheless and should be taken into account. When in "double f5 mode" (looking at your face in third person), stereo sounds are still played relative to the player instead of relative to the camera. This means that when something is approaching on the players right, the sound is still played on the right side, even though the player (or whatever else) is approaching on the left side of the camera.