The main issue is that across my three devices i.e. Desktop, iPad, iPhone 7 (all with latest software), my Photos archive is beginning to show images at Random Dates.
Harri, could you give aan example, in what way you are seeing photos "at random dates"? Are the photos showing different dates on your three devices? Or are random photos appearing among correctly sorted photos? If there are occasionally some photos sorted incorrectly, do they have different filenames from the correctly sorted photos?
i have noticed a few stray photos with strange filenames, appearing out of the blue. These seem to be recovered photos, that should have been deleted long ago and were still found lying around on the Photos library, usually photos in a smaller size, downloaded from shared albums, or previews or other working copies. The upgrading of the Photos Library to the new format seems to have recovered these items. The original photos is usually still there, with the correct date, so I simply delete the recovered items.