AirPods Pro 3: Imbalanced, muffled, ringing audio

I have an iPhone 17 Pro Max (iOS 26.5.2) and a set of AirPods Pro 3 (firmware 8B41). They've been working beautifully together for nearly a year now, but yesterday something very strange started as I was near the end of a long FaceTime Audio call.

All of a sudden, the left AirPod became much quieter. Simultaneously, the right AirPod became MUCH louder, the audio quality in the right AirPod became super muffled (like when you're playing with the EQ on a stereo and turn the treble and mids all the way down while setting the bass to maximum), and the right AirPod started making a very unpleasant metallic ringing / echoing sound.

I ended the call and put the AirPods back into their case to recharge. Unfortunately, ever since then they have continued this sort of bizarre behavior. The left AirPod sound "weaker" or tinnier than the right side, and the right side is LOUD (even when my playback volume is low), the weird tinny ringing / echoing persists, and it seems like the EQ setting and/or volume on both sides is drifting around independently of each other. This happens in all listening modes (noise cancelation, transparency, etc.)

I've done a full reboot of my iPhone and I've done a full "double tap three times" factory reset on the AirPods several times now but the behavior hasn't changed. I've also switched to my Beats Fit Pro's and they sound fine / normal. It's honestly the strangest thing I've experienced with any set of AirPods since the original ones years ago.

Anyone have an idea what could be going on?