Unable to download images from -some- shared albums in Photos

When I try to pull down a single image from my shared album 'xmas 2015' to 'imports'. For the majority of my shared albums, this always works flawlessly. It -seems- that my problems tend to be with older albums. I get the 'shaded in circle' in the header bar of Photos. I tried various other ways to pull the files down too. All I seem to have is the thumbnails for these pictures.

Seems a pretty serious bug, but I'm not sure what to do.

thanks, mike