I have the same problem. Bought my new iphoneX three days back. It was always in the case and had screen protector since the time I bought the phone. I never dropped it and always kept in my pocket. Today I noticed a crack in front of the rear camera and was extremly dissapointed. I am
using my iphone 6s since last 3 year which doesnt have a single fine scratch on complete body, so you can imagine the level of care I take of my device. Now reading this complete thread, I dont see any hope of getting this fixed in Apple Store but will give a try.
Apple Team! This is high time to take some serious steps and work on fixing this problem. With so many users sharing the same experience, there seems to be a genuine design issue.