Photos.app shows wrong picture

I have a weird bug in the Photos.app, where the wrong picture is shown in the full view and the wrong key photo is shown in the People albums.

For instance, when I browse through a particular album in the detailed view, e.g. using the arrow keys, some pictures are replaced by others from a completely different album. Interestingly, the correct picture is first shown for a second (or so) and then it is replaced by a completely different on. Moreover, the new picture is often cropped and not shown in full size, even if the aspect ratio is the same. I noticed that this only happens if faces have been detected in the pictures, but turning "Show Face Names" off does not help.

A second version of the bug appears in the key photos for people's albums. When I select a key photo from an album, sometimes a completely different one is shown in the People overview page, typically showing a face of a different person.

It seems as if the App messed up the index of the photos, but repairing the Library didn't help. I already searched the internet, but could not find any other bug reports of this kind. Is there anything else I could try?

I ended up deleting the entire Photos Library to create a new one. Luckily, all my photos were stored on iCloud and the recognized faces were still associated with the photos after syncing. I have no idea what the cause of the problem was, though.