I’ve also experienced the same problems with the Xs max. A C shaped crack suddenly appeared on the camera lense, the phone has never been dropped and always kept in the genuine Apple case. At first it was two tiny hairline cracks but then the area right around the microphone chipped and spread out a bit more.
I brought it into the Genius Bar for them to take a look, confident from my past experience with Apple customer service that this wouldn’t be an issue. It’s clear to see that the crack has come from the microphone port.
They took it out back and examined it and then came back and refused to cover it under warranty. They insisted that this is due to a point of impact, when I asked them to show me where this was they were unable to show me anything other than the crack coming from the microphone hole.
It is obvious that there is a flaw in the design of the lense, as it shouldn’t crack like this though normal use. I’ve had every iPhone since the iPhone 3G and have never experienced a problem like this before.
I decided not to have the phone replaced and due to this have also decided that this will be my last iPhone. It’s not worth paying the premium over other phones if the quality and customer service is no longer there in my opinion