Ah the dreaded! I had that problem too for one of my projects. The way I get rid of it is to write a custom singleton sfx player script that, when asked to play a certain sound, check if the sound in question is already in play and only plays the sound if is not already playing. Granted I am developing with Godot instead of Unity but I assume same logic may apply. Hope it helps and one day the game can be updated with great level of polish :p