I had posted this earlier this month, but it seems to have "gone missing" on this forum. Here it is again:
"What Apple broke with their High Sierra OS 10.13) public release in October 2017 is rather complex.
It apparently involves Apple iCloud, Google, Contacts, “syncing” replication and update processes, and internet correction “push” update timing/sequencing, possibly also including Calendar.
It is very puzzling, although many (inconvenient) temporary work-around tricks have been accidentally discovered and described by numerous Mac users, internationally. This complexity, unfortunately, makes it very difficult to concisely report details about failure experiences to Apple.
The Apple OS code failure may potentially also create some increased hacking risk to users - which supposedly Apple should take seriously. I certainly do!
Sadly, Apple and Google software does not always work well together, and seemingly neither really cares about this Apple OS software logic and code interaction failure. I am still hoping for an eventual explanation and fix from Apple, Google, or both, but it has already been several months since the issue was reported …"
Also, several years ago I had found an automatic comment in Console which reported an outside "attempt to highjack my AddressBook…". At that time I had been running an Intel iMac with OS 10.6.8. Maybe it was a Google issue even back then, but it had been subverted by Apple until the High Sierra release?
The plot, apparently, thickens!
Best, Bob.