My image files in Media Library appear corrupted

I'm working on a site that has corrupted image files, apparently from an issue with Smush. I have tried restoring the files (but not the database) from a date before the issues began, and it's not helping. Please help!

We have run the regenerate thumbnails and each time, all of the resizes fail. I have a backup from May 22nd (issue didn't occur until May 29th) and it did not repair the thumbnails either. It's not just the thumbnails that are the issue, either. While they are missing in the Media library, any new photos added are not able to be used on the site, it's unable to pull the src portion or of the html for the new photos.