Some photos will not duplicate in iMac
I am using the Photos app on iMac (on MacOS Big Sur 11.2.2) and when I click on a photo and try to duplicate it either using right click, Control + D, or the Image tab certain photos will not actually duplicate. But some will duplicate just fine. I went to my iPhone SE (new version) to duplicate that same photo and it worked just fine and showed up on my iMac as well (all my iCloud devices are connected).
Why would some photos not duplicate on the iMac? Some of these photos are screenshots from Instagram and such. But other screenshots I don't have a problem with.
iMac 21.5″, macOS 11.2