The iPhone XS and XS Max will experience slight animation stutters after about ten seconds of inactivity. This is usually most visible when swiping to go home after reading static content in the foreground app for more than ten seconds without touching the screen. We’ve been tracking this issue for a few months now and the problem continues to be present in the iOS 12.2 betas.
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Seemingly most, if not all, iPhone XS and iPhone XS Max units experience this problem. There have been pages of Apple forum threads since the XS launched in September 2018 complaining about this issue. Someone has even made a dedicated XS Stutter Facebook page to air their frustrations.
Users report observing the problem on all iPhone XS demo units in Apple Stores and some have even gotten warranty device swaps based on demonstrating this problem to Apple retail support staff, but the replacement units have the same flaw.
To reproduce this on an iPhone XS, wait on the same screen and count to ten without touching the screen. Then, swipe up to go home. The animation will skip a frame. A similar result can also be seen launching an app from the Home Screen after waiting for the phone to idle.
Here’s a short demo video of the issue submitted by a 9to5Mac reader:
If you look closely at the demo video above, you can see how the iPhone XS drops a couple frames in the time it takes for the app to shrink back down into its icon. At full-speed, your eye perceives this as a very slight stutter. We have compared side-by-side with an iPhone X using a slow-mo video and the XS misses a frame of animation very consistently, whereas the year-old X renders correctly.
The frame drops don’t happen if the user has been actively using the phone, there seems to be a timeout of about ten seconds. After that wait, the first interaction lags behind the user’s finger … and then catches up. There is speculation that in the A12’s chip transition out a low-power state, it cannot keep up with the initial touch. However, neither the iPhone XR — which features the same A12 chip — nor last year’s iPhone X experience the same problem.
When the multitasking gestures debuted with the iPhone X, Apple made a big deal about how fluid and responsive they should feel (including doubling the sample rate of the touch screen to 120 HZ.)
The good news for iPhone XS owners reading this is you might not notice the problem, even if it is going on. It is very subtle, lasting only a fraction of a second, so many people are unlikely to spot it — even if someone else points it out.
For people that are sensitive to this kind of stuff, though, it is understandably very annoying and clearly not working as intended. You can classify it as nitpicky — but customers spending $1000+ on phones naturally have high expectations of quality.
The issue has persisted through iOS 12, iOS 12.1 and the latest iOS 12.2 beta. Users on forum threads suggest a variety of workarounds from disabling the FaceTime app to enabling AssistiveTouch, with varying degrees of success.
Hopefully, Apple can address this in a software update. As stated above, the iPhone XR does not have this issue which implies that a software fix could resolve the problem for iPhone XS and XS units.