Issues with Photos application after update to Sequoia 15.0

I store my photos library on an external hard drive, and after the Sequoia update, many of the photos that were

available previously, are now corrupted. These photos came from many different sources, DSLR camera, iPhone, e-mails from family, etc. It doesn't seem to matter the source of the photo, but before the update, they all worked fine. Now, when you pull them to the desktop to attach to an e-mail, post to Facebook, or anything else you might do with them, there is no image when you pull it out of Photos. You can see the image in Photos, but nowhere else. The really confusing part of this is that you can have a hundred consecutive DSLR images in the file, and maybe three of ten will work fine, the others will not...

Has anyone else seen such a thing? I need help here.