Guild Wars 2

Every time I fight him I am about to take him down he just walks back to where he originally was located and heals his full hp, at this point he just walks back and kills the npcs assisting in the quest leaving me to attempt to solo it where that is impossible for me, so when I replay the mission the same thing happens he has about 20-10 percent of his health and he just casually walks back to his spawn and kills everyone.

Same thing happening for me. He randomly ports all around the place and then when he starts taking a few hits he resets to his spawn point at full HP.