I encountered this almost all the time from two Horntail runs - whenever Horntail would 1/1 my Shadower while MG is active, the pet would almost never auto-heal, and instead leave me at half hp. I tried changing the hp slider all the way down and all the way up, and it had the same effect each time, constantly failing to pot when she is hit with a 1/1 and MG buff is applied. I wasn't using any buffs while the 1/1 was incoming, so the pet shouldn't fail to auto-heal like it would if you were to caste any buff while receiving damage. Not urgent but worth looking at eventually ^^