AirPod Pro Feedback Over the Phone

When using my AirPod Pros to chat over the phone, the person on the other end of the line hears an intermittent high-pitched squealing noise that is loud enough to drown out everything else. The actual wearer of the AirPods doesn't hear anything. This makes them unusable for phonecalls.

Details:

• This happens when they are in both noise cancelling and transparency modes
• AirPods have never been exposed to water and are clean
• AirPods are fully charged
• AirPods aren't being covered or under any pressure
• First generation, model A2084
• Firmware version 6A321

Any ideas of how I can fix this?

Thanks!!