Some macOS High Sierra users are reporting delays in receiving iMessages on their Macs, while also finding that they are no longer receiving iMessage notifications on their iOS devices and Apple Watches …
That latter fact suggests that the bug may be related to Apple’s plans to offer iCloud sync of messages later this year.
With iCloud synchronisation of iMessages, deleting a message on one device would delete it from all, rather than the current halfway house of messages being sent to multiple devices but each thread remaining otherwise isolated.
AppleInsider first spotted a 4-page thread on Apple’s support forum. A Radar bug report classifies it as a serious bug, but one that is only sometime reproducible. The bug report does not reference delayed delivery to other devices.
My messages experience has been horrible since upgrading. iMessages give zero alert. I have my phone sitting next to my Macbook and neither notifies me when I get an iMessage. I have to manually click the home button to see if I have received any messages. Only when i shut down the Macbook does the phone start responding with sounds + vibrations.
Those who are experiencing the delay are reporting anything from minutes to hours. Users report mixed success with a range of measures, such as signing out of iCloud on the Mac, but downgrading to Sierra is the only thing that seems to work for all.
The latest beta of macOS 10.13.1 was released to developers yesterday, with a focus on bug fixes and performance improvements.