Reports have started to surface of customers complaining that their iPhone X rear camera lens covers are cracking, even though they haven't been dropped. Apple uses sapphire crystal for its lens covers which are resistant to scratching, but are more susceptible to cracking under pressure than Corning Gorilla Glass.
https://www.notebookcheck.net/Lensgate-is-the-iPhone-X-camera-lens-cover-susceptible-to-cracking-in-normal-use.305892.0.html
On my iphone xs, the camera backing came off fully. i got it fixed but with 2 weeks the back came off again!