Sound volumes randomly fluctuating

Platform: Windows
ISP: Comcast
Type of Internet Connection: Cable
Internet Connection Speed: 25Mbsp
Date & Time: April 30th
Frequency: Often
Character Name: Gameesh
Race: Galka
World: Phoenix
Main Job: Summoner
Support Job: White Mage
Area and Coordinates: Port Bastok, in front of the Odyssean passage
Party or Solo: Solo
NPC Name: None
Monster Name: None
Steps:
1) Engage a fight
2) After the battle is over the sound effects volume will be really loud, yet music is rather soft.

I did a speaker test and the hardware + software function properly. I also listened to some music and played a few other games. No issues in volume changes.

Changing the in-game volume balance doesn't do anything.

A rather weird but very annoying issue. I hope this can be fixed somehow.