I'm not too surprised. Flying animals use a couple of tricks to appear flying, but the game isn't designed to handle that so some visual errors do occur. The Beach Tanks Expanded should have less jittery flying animals since the water area is considered one volume rather than four overlapping volumes as it is in this tank.

Nice, but I've noticed a small issue with the Doryg from your Jurassic collection. When it's flying around, it teleports around the tank to get to its next movement loop. Kind of weird!