In short, I had found 5 Berserkie cards at one point today and completed the set, A few minutes afterwards upon picking up another card from Ulu I, which I assume was a Berserkie card (though I don't know if cards from a completed set keep dropping) I looked back at the Monster Book and found that the Berserkie entry was reset: (Can confirm that prior to the sixth card, this set was listed as completed at the book, I just didn't take a screenshot) Also I scrolled through the pages and found a card that I neither collected nor hunted for:
This should be fixed as of this server check that we just had. The cards' levels were being stored correctly, however the client seems to not display card levels correctly when using the special space-saving Monster Book data format in combination with our custom cards. With the fix in place, you should now see the correct cards (i.e. whatever you picked up in the first place, before they were switched around) - let me know if that's the case!