I assume that the information in the "In Library" column tells you how Calibre matched the books on the device with the books in the library, which is probably different between the initial copy and subsequent connections. I think I've only ever seen UUID there, at least if the book is already on the device. As far as I understand it the plugin isn't involved in this at all, so any weirdness that you're seeing should be due to Calibre itself. Odd that double-clicking on it works for you though while I'm getting an exception.
Edit: Of course @chaley posts the explanation just a minute before me