Whenever I play several sounds at the same time I get glitches in the sound, or some of the sounds play at a lower volume.
I’m probably doing some noobishly wrong, would love to get a direction as to what that might be. 
It could be a performance issue.
Have you checked the profiler while running the app? In my experience, that issue happens when fps gets very low, or somewhat unstable.
Is it the same sound you’re playing? When you play the same sound or similar sounds over the top of each other they become amplified and often distorted.
You need to look into audio mixers and coding an audiomanager that will prevent the exact same sound being played in the same frame.