Hmm, not sure i've seen this bug before. Is there any way you can record a vid of it happening and send it over? The sound should slow down when you hold a burst, but it shouldn't sound that wild I don't think.
Turns out it was just a problem on my end, due to the game lagging and the audio repeating certain sections of the song whenever I would hold a burst; the slowed-down audio simply lags, causing it to sound like the gates of hell. This problem thankfully doesn’t occur anymore, but I sadly didn’t get any footage of it when it would.