problem of photo size unknown

I use the theme matrix, almost everything is fine until this afternoon some photos have problem of photo size unknown after I did "Delete database cache" and "Build all thumbnails/resizes" (I can't remember what I did exactly in "Maintenance" when this just happened.)(I set the thumbnails to 200 and Resized Images to 640x640.)

The problem is like this:

In "size" selection dropdown menu, it changed from:
640x425
4288x2848
to:
unknown
4288x2848

I also added "Item actions" in the sidebar, it changed from:
Download Photo (200 x 133)
Download Photo (4288 x 2848)
Download Photo (640 x 425)
to:
Download Photo (0 x 0)
Download Photo (0 x 0)
Download Photo (4288 x 2848)

I tried "Delete database cache" and "Build all thumbnails/resizes" again, problem still there. And I deleted the photos with problem and uploaded again, no problem.
But there are a lot of photos affected by the problem (almost 20%), I can't do it one by one, anyone has any idea to solve it?

Thanks