@Anthro-Cheetah Oh wow. That is super interesting. I didn't realize HDD speed could affect audio.
I've only got my internal XBOX HDD. No external HDD connected. I tried reinstalling PSO2 this morning. Unfortunately after running around the lobby for a bit the issue occurred again.
I've looked through the settings and it doesn't look like XBOX has any sort of HDD clean up or optimization tools like the PS4 has so i guess theres not much i can do to try and speed things up any further HDD wise.
I've actually got a spare 500GB SATA3 SSD laying around. Looks like it's pretty easy to replace the HDD inside the One X. 500GB isn't much space though. 1TB SSD's are still expensive. Might as well buy a series X if i was going to buy one of those. Maybe I could install the 500GB SSD and buy an enclosure for the current 1TB drive and connect it with USB.
The HDD speed has to be the reason this is happening though, that's really the only thing that can be variable between consoles as everything else is the exact same spec wise. So this would explain why this issue is not happening to everyone. I guess i got unlucky with a defective HDD or something
Thank for your insight and info! At least i know the reason now.