Permission Denied for a small set of photos when adding to macOS Mojave Photos

I've got all of my digital photos (roughly 112K files) on an external hard-drive. With the changes made between Google Photos and Google Drive sync, I'm now moving my photos into iCloud Photos via the macOS Mojave Photos app.

I have a single folder, from 2007, that I've run into that has 855 photos in it. 41 of them cannot be processed. When I try to add the photos to the Photo app it tells me that I do not have permission to view the photos. I do have permission though, I can open them in Finder, make changes to the photos, copy/paste or rename them.

I've looked at the permissions and I have read/write set. What else might be preventing the Photos app from allowing the photos to be added? I can go to the Google Photos site and download the same photos back onto my local machine and they still won't get added to macOS Photos. There's something weird with this specific set of photos and I don't know how to resolve it.

All previous photos for 2007 were taken with the same camera - I verified that with the EXIF data on the photos for the year. I assume that rules any file format concerns out but I'm not confident enough to say that's not the issue though.

Any one have any suggestions?

EDIT

I've also opened the files in Preview and exported them from JPG to HEIC, PNG and JPEG thinking that writing a new file might fix any permission issues. It didn't help. I'm wondering if this is something more than a permission issue but I don't know how to troubleshoot this.

I'm not sure what caused the problem. I went to iCloud.com, opened Photos and was able to upload several of the bad photos without an issue.

I shut down macOS Photos and re-launched it after it had completed syncing the batch of files it was syncing to iCloud. Reopening Photos had the bad photos I tested on iCloud.com sync down without issue. I then imported the rest of the bad photos and they were added successfully.

I assume something was messed up in Photos and a restart was needed.