Apple didn’t specify a cause for the issue, but affected units could have problems with the follow:
“An affected AirPods Pro may exhibit one or more of the following behaviors:
- Crackling or static sounds that increase in loud environments, with exercise or while talking on the phone
- Active Noise Cancellation not working as expected, such as a loss of bass sound, or an increase in background sounds, such as street or airplane noise”
Apple’s repair program doesn’t extend the warranty on the AirPods Pro, but covers replacements for one or both buds, if necessary, for two years after they were first sold. If you’re having issues, contact Apple Support, an Apple Store, or an authorized service provider so they can check them out.