Issue with images which have no sizes available

I’d say it’s a Database Issue. If it were the actual image it wouldn’t show up. I’ve had the same issue before but with only a few images luckily. I believe it was caused by a database error. I was having issues on the shared server at the time, and imported quite a bit of content from another site I use for testing. If you have a back-up of the Database you can try restoring the DB to fix the issues. I ended up re-loading the images since I had so few.