Today I tried uninstalling and reinstalling the latest audio drivers from my motherboards vendor. Also disabled Windows' 10 Game Mode and disabled "full screen optimisations" so the game ran in the old classic "Full Screen" mode. Browsing through Firefox caused game to lose sound again. After this I have nothing else to try. I couldn't run the game to a more "stock like out of the box scenario". The game just drops sound out of the blue and this happens only to this game. There must be something wrong in the background with the game's audio engine that I can't see. The only scenario that I can somehow replicate or create the circumstances for this to manifest is by browsing websites with Firefox and ALT+TAB between Firefox and XIV.