MacRumors:

Apple is today releasing an updated version of iOS 12.1.4, which is designed to address a major FaceTime bug that was widely publicized last Monday. The new update comes two weeks after the launch of iOS 12.1.3, an update that introduced bug fixes.

The iOS 12.1.4 update will be available on all eligible devices over-the-air in the Settings app. To access the update, go to Settings –> General –> Software Update.

If you use or want to use Group FaceTime, update as soon as you can.