Every iOS update seems to affect Apple Pay Suica performance. For me iOS 11 still does not match the rock solid Suica Express Transit performance of iOS 10.3.x on iPhone 7. The iOS 11.2 update went smoothly for the first few days, then Apple Pay Suica notifications (shown below) stopped working the same time that Apple Pay Cash went live in the USA.
Apple Pay Suica still works but none of the iOS 10 workarounds to revive Suica Notifications work anymore: Suica Help Mode +Restart, delete and reinstall Suica in Wallet, etc.
I also notice that after updating to iOS 11.2 iPhone X experiences “gate flicker”: the station gate flashes red for a fraction of a second then clears. The last time I experienced gate flicker was the iOS 10.1 rollout of Apple Pay Suica service in October 2016. I guess that means performance has regressed a bit and suspect it is connected to the NFC related issue mentioned earlier JR East store reader error notice.
Japanese twitter users are complaining about sluggish iOS 11.2 Apple Pay Suica performance, gate errors and the dead Suica notification problem appears to be widespread.
Hopefully Apple Pay Suica performance will get a proper tune-up in the next iOS 11 update.
UPDATE 1: Read about the iPhone X Suica Problem
UPDATE 2: The iPhone X Suica problem may be a NFC hardware flaw. Details here.