Iguanadon Feet Auto-Locking up onto Marking Trees

On Iguanadon in certain positions one or both limbs will auto-lock onto the underside of the marking tree.

On Iguanadon: I walked up to the marking tree on the right side (Dry Fang Canyon, near the Waystone) and my Iguanadon's back left foot moved through itself directly up and latched onto an invisible plane on the underside of the tree. The same thing happened with moving under the tree facing forward and both front legs went up in the same way.

I expected the dinosaur's legs to stay firmly on the ground, not meshed up through itself and facing the sky.