Every iOS update seems to affect Apple Pay Suica performance. For me iOS 11 still does not match the rock solid Suica performance of iOS 10.3.x. The iOS 11.2 update went smoothly for the first few days, then Apple Pay Suica notifications (shown below) stopped working just about the time that Apple Pay Cash went live in the USA.
Apple Pay Suica still works fine 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 occasionally 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-F timing issue in the earlier JR East store reader error notice.
Some Japanese twitter users have complained about sluggish iOS 11.2 Apple Pay Suica performance
but fortunately and the dead Suica notification problem appears to be widespread an edge case: me and the other guy on Twitter.
Hopefully Apple Pay Suica performance will get a proper tune-up in the next iOS 11 update.