I have had a baffling and very frustrating experience with Photos in the last few days.
A couple of days ago I asked Under what circumstances could Photos delete a large number of albums without warning or indication?
I added a large number of photos to Photos, and allowed it to upload them to iCloud.
At first, all was as expected, in Photos, on iCloud.com/photos, and on other devices attached to the same account.
Then multiple albums (not the photos in them, just the albums) disappeared, across all devices and iCloud.com/photos. In some cases I watched this happening before my eyes.
Since then, on one device (an ancient iPad running iOS 9.3.5) most of the missing albums have reappeared. On others and on iCloud.com/photos, a few missing albums have reappeared (but nothing has changed for about 24 hours).
What is the source of truth? If it's iCloud, why doesn't iCloud.com/photos show the missing albums, and why did the iPad find some of the missing ones before iCloud did?
What processes are occurring, and where? I don't see any sign of relevant activity in Activity Monitor, or in Photos, or on iCloud.com.
Is there some way of hastening the process of synchronisation, if that's taking place, or even finding out what is happening behind the scenes? What are the processes, that that mean albums can mysteriously disappear and reappear?
The one saving grace is that so far, all the actual photos seem to be safe, but I have lost a great deal of faith in Photos and iCloud over this.