Apple investigating subtle issue on the iPhone XS and iPhone XS Max that has users upset and annoyed
A number of posts have been made on Apple's discussion website in reference to a problem found on the Apple iPhone XS and iPhone XS Max. After either model is inactive for a period of ten seconds or longer, animation on the screen stutters when users scroll, or swipe up on the display to close an app. This is not a new issue either since some of the posts date back to October. An entire Facebook account is dedicated to the issue.
Apple apparently does know about this problem since some iPhone XS and iPhone XS Max owners were able to receive replacement units under the terms of the warranty. But the models sent by Apple also stuttered as well. One community member claims to have received two replacement units and both of them suffered from the same issue. It is interesting that no stutter has been detected on the iPhone XR, nor is this seen on 2017's Apple iPhone X.
The reason for the stuttering is unknown. One theory is that because the A12 Bionic chipset powers down during the period when the phone is inactive, it fails to pick up the user's initial touch input. An Apple Store employee reportedly told one iPhone user that the phones were not calibrated correctly.
A video taken by an iPhone XS user (via 9to5Mac) shows that the animation drops a couple of frames when the calendar app is closing, shrinking in size before it retreats back into the calendar app icon. While this seems like a minor problem that you might not notice at first, several iPhone owners say that it has become a distraction and annoyance to them.
Beta versions of iOS 12.2 have not fixed this problem, and Apple says that it is investigating.