Apple has acknowledged a microphone issue affecting a limited number of iPhone 7 and iPhone 7 Plus models running iOS 11.3 or later.

In an internal document distributed to Apple Authorized Service Providers this week, obtained by MacRumors, Apple said affected customers may experience a grayed-out speaker button during phone calls. The issue may also prevent affected customers from being heard during phone calls or FaceTime video chats.

It’s always fascinating to me how these types of issue only affect a small number of users using a certain model. I’m not being sarcastic, it’s honestly an interesting phenomena.