Having trouble with iPhoto. The Faces part was working properly, but not having these symptoms:
1. When I select Faces, the people shown are not the one showing in the thumbnail in some cases. Opening the picture shows the individual is in the photo, the info tab shows the person is in the photo, but the photo does not show the person.
2. When I select Faces, sometimes the face shown is not the correct face.
It used to be perfect, but now it is not.
I've used all the options within iPhoto under Option & Command start, and have rebuilt it using iPhoto Library Manager.
I had and still have the same problem. Here is what partially soved it for me.
1. Go through all your photos for one person. Flag any that have a problem.
2. Open Flagged album.
3. For each photo delete all found faces.
4, Select all Flagged photos, then Photos > Detect Missing Photos.
5. Open each photo and assign the correct name to the found Faces.
When the original found faces become corrupt no rebuilting by iPhoto or iPhoto Library Manager will fix the problem. Deleting the corrupt found face boxes, then redetectiing the faces creates uncorrupted data structures.
A major problem is that the data corruptions appears to be associated with the photo and not restricted to the found faces which have obvious issues. If you delete only the incorrect found face boxes but leave those which seem correct, I have observed that applying Detect Missing Photos may result in the originally correct found faces being changed to have something wrong.
Another problem is that if you delete a correct found face box and then applying Detect Missing Photos finds exactly the same box, iPhoto remembers you have deleted it and does not replace it. In my hands this has happened in about a quarter of the photos. At least some of my photos have been repaired.
An observation that may confirm we are seeing similar coruption is the shape of the incorrectly placed found face box. In many cases I have seen a vertical rectangle which is offset from the found face. For different corrupt found faces this rectangle may be in differnt places in the photo, or of a different size, but the height to width proportions seem similar. Do you see found face boxes like this?