Quest Sounds not changing

Trying to adjust the sound settings, I found the collection musical stem that plays upon completing a quest to be rather loud and wanted to turn it down, only quest audio doesnt change anything? I turned it all the way down to 0 and could still hear myself collecting things and could still hear the sound of a completed quest, as if it was still at 100% {though i have it turned down to 80, i've realised its useless and it doesn't change at all}
All other audio toggles do change, music gets turned lower/off completely if you alter it, sound effects get turned down such as wind or animal noises, but quest audio doesnt change anything. I was hoping to ONLY turn down the completed quest sound as it's far too loud {in my opinion} but still want to hear the collecting sounds. Would there be a way to have this changed in the future?
The sound of collecting quest items comes under "Effects Audio" but the musical sting for completeing quests/ having the ticker go up, doesnt change under anything.

Could still hear 'Quest Audio' when turned down to 0, doesn't change sound output for any quest related sounds.

For Quest Audio to get quieter or go away completely if you change the slider volume.