Whenever the monsters (balron, ancient wym, etc.) is redlined on uneven landscape, near the water or a player's house, they will fly around trying to avoid the damage. Instead of following them, my pet (including summoned earth eles) will just step away a few tiles and walk back and forth on the same spot; or walk into the player house and do nothing. I think it is related to the pets failed effort to pathfind the monster that are flying in the middle of the air. So each time the monster is in air, the pet will go nuts. Talk about annoyance! Then sometimes, the monster will fly away on the water and stay there to regain health. How smart! The problem is it won't come back land even after it gets back significant amount of hp. Of course, my tamer can use spells or bows to kill the monster after my pet goes nut, or I can use a boat to get close to the monster on the water. But the question is: are they behave as designed? A more common buggy situation is when you kill the monster who happens to be flying in the air, or stuck on high ground, or on some uneven terran, you can't loot it. I believe all these issues are related to the Z axis.