Maybe it's just the version then. I know some others on Zoo Admin have the problem (I don't know whether they're from the same country, ie if UK game has differences to the US) and I had it before and after the latest patch. (Only challenge games, since it's triggered by certain challenges)
After a bit of experimentation it is definitely only when you get new animals delivered to your zoo... so a work around would be just to avoid those challenges, but I'd still like to have em, y'know? And it was a whole lot of hassle before I figured out that it actually WAS them. So far it's only been with the mystery animals and mate-within-1-2months challenges, haven't tried the jungle one, insane-cost-mystery-animal, or zoo-swap-animals challenges.