Sync between iOS and Mac Catalyst is intermitent. The fundamental issue is slow and inconsistent remote notifications being sent to and received by the Mac Catalyst app.
When making changes in the Mac Catalyst app, those changes are successfully pushed to the iCloud private database and the iOS or iPadOS app successfully receives the remote notification indicating the change. In short, the MacOS -> iOS direction is seemless.
When making changes in the other direction, we run into problems. A change in the iOS app successfully gets pushed up to the iCloud private database, and other iOS or iPadOS devices successfully receive the remote notification. However, Mac Catalyst apps most commonly will not receive the remote notification at all, or – occassionally – will receive it several minutes after the change took place. Rarely will the Mac Catalyst app receive the notification in a timeframe consistent with the performance of iOS apps (within 2-4 seconds).
Why are Mac Catalyst apps having so much trouble receiving these CloudKit-triggered remote notifications?
(Note that these issues are present in both development and production environments.)
