Bizarre Monster Book Error

I don't think picking up the new cards messes up your monster book at all. My Skelegon cards say I have 1 even though I have them maxed, but when I found yet another Skelosaurus monster card yesterday it deleted itself because I apparently already have them maxed. Meaning the game knows that I still have maxed Skele cards, but the monster book is simply showing me the wrong information.

Most likely your monster book data is stored as a series of bytes and read in a particular order. The client side display data hasn't been updated, so it's spitting out unpredictable numbers that don't match what you actually have.

Something similar happened to me, but it was because I hadn't relogged since my last card. When I next relogged, the card that disappeared was marked as max.