Elements 14: Organizer: In the grid view, there photos which do not open and show the hourglass symbol

I have Photoshop Elements 14. When in the grid view, there are several photos which do not open and show the hourglass symbol. When I try to open the individual picture, I still get the hour glass symbol. When I go to the side by side view and can view the picture just fine. This is happening on only about 10 % of the photos in my catalog. Any ideas?