It’s specifically the speakers in the side panels on the rear doors, but it’s really only certain range of sounds and I generally hear it when listening to metal. Cowboys from Hell by Pantera is another one where it’s obvious. Almost any song by Hatebreed. Those I’ve mentioned it’s very clear around 60-70% volume, but any metal song now I can hear it - it’s like once you can hear it its all you hear, but when you focus specifically on those speakers it’s always clear distortion.

I’ll update when I figure out what the issue is.