Audio balance incorrect in Frontline following today's patch

Date & Time: 23rd May 2023 11:30am BST
Frequency: Always
World name: Yojimbo
Character name: Renard Lefeuvre
Class/Level: Tested on BLM/DNC, likely to be the same on all classes
Party or solo: Party
In-game time: Any time
Area and coordinates: Any location
Steps:
1. Set system volume to 100% for all sound effects other than BGM, which is set to 66% so that I can hear sound effects over the music. This has always worked perfectly everywhere in the past.
2. Join Frontline Roulette (today's was Seal Rock/Seize, I am unable to test elsewhere due to the nature of Frontline).
3. The BGM in Frontline is nearly inaudible. Sound effects etc are at 100% volume, as intended, but the Frontline instance BGM sounds more like it's set at 1%. I used to be able to hear it fine, since today's patch I cannot. If I change my system settings it will be correct (I hope?) for Frontline but wrong everywhere else. Frontline maps need to respect the player's audio settings and play the BGM at the correct (audible) volume. I believe the current implementation is a new bug.

It is difficult to test further because I cannot visit the Frontline instance without being in a 72-player game with a timer and objectives which do not lend themselves well to experimentation, but I have played Frontline hundreds of times and know how it should sound on my system. The music is gone.

Connection Specs
- Type of internet connection/provider: Gigabit cable connection
- Modem maker/model number: Irrelevant to bug

■ PC Specs

N/A

-=-=-=-=- System Information -=-=-=-=-

■ PS5 Specs

Model Number of the PlayStation®5 You Are Using
- Model Number: CFI-1000A.