AirPods Pro 3 Active Noise Cancellation degrades after a few minutes on firmware 9A348

Hello everyone,

I am experiencing a very specific issue with my AirPods Pro 3 (Firmware version 9A348).

When I am at the gym, the Active Noise Cancellation (ANC) initially works perfectly, completely blocking out the heavy bass and low-frequency noise (like gym music, heavy weights dropping, or treadmills). However, after a few minutes, the ANC suddenly degrades and starts leaking a significant amount of external low-frequency sound/bass into my ears. My own music still plays fine with good bass, but the external noise cancellation simply fails to block the gym's background low frequencies.

What I have already tried:

• I performed a factory reset of the AirPods.
• All smart features like Conversation Awareness, Adaptive Audio, and Loud Sound Reduction are completely turned OFF. I am using pure ANC mode.
• Ear Tip Fit Test is green (Good Seal).

Temporary fix: If I manually cycle the ANC mode (switch to OFF and then back to ANC), it fixes the issue, but only for a minute or two before the low-frequency leak returns.

Has anyone else experienced this phase-synchronization or calibration drop on firmware 9A348? Is there a known fix, or should I take them to an authorized service provider for a replacement?

Thanks for any help!