This was during the level 80 monolith version fight I noticed that Lagon took no damage from my Wandering Spirits and just passively stood(?) there and let me attack him.
This was in both Phase One and Phase Three of the fight.
Did you do a search for this one… Sounds like the Lagon fear bug where he stops doing anything if he has been feared… There is a thread about this somewhere… (too lazy to search… sorry )