My case was using an external SSD and getting the import error on certain images. I realized if I opened the image in Preview and saved it then I could import those images without issue. I thought maybe using something like touch in the Terminal would work to update the modified date of the file but this didn't work. What did work was simply copying the files. Either copying them to a new location on the external SSD or from the external SSD to my internal storage. Both scenarios worked. I'm guessing there is some file metadata that is changed or written during this process. Annoying but at least it worked. Hope this helps someone else out! TL;DR Copy the image(s) and then attempt to import the copied image(s). Copying an entire folder with images works as well.