Exporting an Album - counts don't add up? Missing 1000s of photos

I have been test exporting a album with 9500 images to a external HD for "safe keeping", I select the album, select all photos and export to the external HD.  Progress looks good, 1 of 9500, etc, a day later 9500 of 9500 - yay done....

However the issue - on the HD - export folder, there are 1675 images exported.

So - the mystery....   where my the other 7700 images be, they are in the album....

This sort of stuff drives me crazy, I was finally feeling like CC might be the tool to move to, now i have this mystery.

Jeff