AirPods Pro audio randomly fades after upgrade

I have just upgraded from EarPod pro to EarPod pro 3. 1 day ago. When connected to my iPhone or Apple TV the audio fades randomly for between 5 and 30 seconds. It’s still audible but muted so much it can hardly be heard. I have tried all of the noise cancelling options including off and it is still the same.

is this a fault or can I fix it by adjusting a setting?