Even though iOS 18 has only been available to the public for 48 hours, a significant bug has been found, as reported by 9to5Mac. This bug involves iMessage and sharing Apple Watch faces with others, and the only way to fix it requires some data loss.
For now, the best action to take is to avoid triggering the bug within iMessage. It is produced when you reply in a threaded message to a shared watch face link, with an example provided by 9to5Mac below. This triggers iMessage to crash if the user tries to open the conversation repeatedly, and it can crash even when opening other conversations, which affects both users.
Currently, the bug is only triggered when responding from iOS 18.0, as replying from iOS 18.1 does not trigger the bug. This doesn"t mean that that version is immune. However, if it has been responded to, then the app will still crash on iOS 18.1 beta, iPadOS 18.1 beta, and macOS 15.1 beta.
The quick and immediate fix is one that many people will not want to use, however. It requires deleting the entire conversation thread from each device. This removes the conversation history completely, including photos and videos that haven"t been saved outside of Messages. Restoring the thread from the recently deleted location will reintroduce the bug.
For the time being, the best thing to do is not to reply to a shared Apple Watch face in a thread at all until Apple issues a fix. This follows reports that surfaced yesterday about iPadOS 18 turning the latest M4 iPad Pros into nothing more than very thin paperweights. Even though the software has been in beta for a couple of months now, it appears that some bugs have managed to slip through the cracks.
Source: 9to5Mac