Old photos in Photo Stream
I have all the photos I take on my iPhone upload to my Mac. Why are 5 year old photos suddenly showing up in Photo Stream on both phone and Mac?
iPhone 12 mini
Question marked as
All photos on your device, that have recently been added to Photos, will appear in My Photo Stream and be synced to your other devices.
Sometimes older photos will become orphaned in your PHotos Library and no longer be linked to the thumbnail for browsing. When Photos has to rebuild a library after a Photos Library gets damaged or upgraded to a new system version, Photos will colect orphaned items and show them in a seperate album or folder "Recovered items". My PHoto Stream will treat these recovered items a new photos and you will be seeing them again on other devices.
Frequently these recovered otems are duplicates and can safely be deleted.