Hi Martin @techsupport, yes, you’re right, I usually use my iPhone. It’s not so bad now, but still happening quite often.
I think you know how the photos are organized on an iPhone. If I post the pictures from the “Recents” album they usually work OK. However, if I use a sub-album, in this case Superleggera, they fail more often. Hope this makes sense.
Thanks as ever for your help.
George