So, since flying mounts have been able to be used as ground mounts, certain mounts using the drake model have had a bugged animation when jumping, or specifically, when landing from a jump. I know this affects at least the Gladiator reward mounts from Cataclysm, but I believe it also affects the Gladiator reward mounts from Wrath of the Lich King.
When using the affected mounts as a ground mount and jumping, the animation will bug out upon landing. As soon as you hit the ground, the mount will jerk back in the air and then back to the ground. The rider of the mount also rocks forward and backward during this animation bug.
This bug existed in other mounts using the drake model, such as the mounts that dropped from the Deathwing encounter in the Dragon Soul raid, but was fixed. I imagine that because much fewer people have access to these gladiator mounts, the bug has not been reported enough to get fixed. Here is a brief video of the bug in action: