Apple recently released iOS 16.4.1, and as is traditional, has now stopped signing iOS 16.3.1, making downgrading to that version of iOS no longer possible. iOS 16.4, iOS 16.4.1, and the iOS 16.5 beta remain signed at the time of this article.
iOS 16.3.1 brought multiple bug fixes, addressing issues with iCloud and Siri requests for Find My, as well as more Crash Detection optimizations.
The new software can be downloaded on compatible devices over the air by going to “Settings” -> “General” -> “Software Update.”
Falling back to an older iOS build is often used by users that jailbreak their iPhones. Restoring an iPhone or iPad to a previous version of iOS can also sometimes be helpful for users who experience significant bugs after upgrading to the latest version of iOS.