After online reports of a bug that appeared to be crashing iPhones just after the date rolled over to December 2, Apple rolled out the iOS 11.2 on Saturday, the first time the company has ever released an update on a weekend. Time-based notifications for certain apps began crashing or respringing the devices at 12:15 a.m.
on December 2, specifically apps that issue repeated reminders throughout the day. Apple took the unusual step of releasing its iOS update on the weekend to remedy that issue, but seems to have rushed it out with some parts not operational.
Apple Pay Cash, the method for using Messages to send person-to-person payments, is included in the release but not yet functional. Users have also reported problems with Face ID in iPhone X after updating, but most have found a reboot after installation clears up the problem.