Since Head of the Snake patch, the Guardian boss in Spirit Vale has been bugged. It will not path correctly to the tank. At random intervals he will run in a line back and forth to no one, sometimes in circles, etc.
Another thread talked about this, but I decided it needed to be put in the “bug” section.
Here’s a link to the other post.
https://forum-en.gw2archive.eu/forum/game/dungeons/Vale-Guardian-Running-in-Circles