it sound like you are overloading the sound buffer.
that happens when you trigger A LOT of sounds together.
you must take care of sound triggering to avoid that.
sometimes you are triggering a sound with an overlap and because of the nature of the overlap it triggers a lot of times and causes that problem
other is like having for example actors with miniguns firing all at the same time and each shoot plays the bang sound…
I use to spawn sounds (disable auto destroy so they dont die on end, stop on spawn so it doesnt sounds yet) and store in variables or arrays…then I control my sounds somehow and this way I am sure I am not overloading some buffer causing that not sound at all event.
(think if you have a lot of firing happening at the same time but you only hear 3 or 4 fires together you will not notice)