I've tried deleting the photo from photobucket and renaming the original source photo and reuploading. (kristinabraly.com)
It's a million times easier to source your photos correctly from the start than to replace them later because of permission issues. (ebookdesignworks.com)
And the time the comparisons take could indicate something about the source photos: Photos of obviously different people could be easy to rule out, but photos of very similar people might take longer to distinguish. (sciencedaily.com)