Hey mate, here’s a few troubleshooting tips but, if it doesn’t work, I’d suggest logging a ticket with CMF Support here https://cmf.tech/en-gb/pages/support-center as they’ll be able to guide you if the item is faulty. Here are some troubleshooting tips:
Are you running the latest software?
Have you tried switching out the earbuds to a smaller/bigger size to test?
Have you tried resetting the headphones in the Nothing X app?
Have you testing this across multiple devices and is this consistent?
Is this occurring across every app? At any volume?