Volume locked at max when headphones are connected (Steam Deck OLED)

[i0nium]

Your system information

• Steam client version: 1769025840
• SteamOS version: 3.7.19
• Opted into Steam client beta?: No
• Opted into SteamOS beta?: No
• Have you checked for updates in Settings > System?: Yes

Please describe your issue in as much detail as possible:

When playing games with headphones plugged in, the volume sometimes becomes maximum and system volume controls have no effect. (Volume UI slider responds normally, but audio remains unchanged.)

Steps for reproducing this issue:

1. Open a game with headphones connected.
   (Katamari Damacy Reroll has a high recurrence rate)