I export my pictures from Lightroom via SFTP and once had the case (2 years or so ago) where a newly uploaded picture had the same name as an existing one and all of a sudden, an old post showed a new picture. ??
To clean up, I
- re-uploaded the original picture to the same folder, overwriting the new one again
- imported the metadata of the mixed up image
- recreate the thumbnail
- (not sure about this) delete the NGG cache to clear mixed up dynamic images
- changed my file naming pattern to include the original name and the date, so this would never happen again.
Also when I’m uploading new pictures and before adding it to an article, I notice that for example it looks too dark, I just upload the same picture again (SFTP) and recreate the thubmnail. Works fine.
Not sure about the gallery upload UI, I never use that.