I recently took a number of books to a local con to get them signed, many by multiple artists, and have noticed that, when I am trying to add a creator’s signature to books, it deletes the previous indicators that the book has been signed by someone else. So for, I’ve been able to go back and re-add those signatures at the same time as when I add the one, but that’s a long and tedious workaround.
Sorry to hear you’re having troubles with this. Can you show me this in a video? I’m assuming this is on your Windows computer, in the old Comic Collector software?