This bug occoured after the escorting waypoint to Crystal Bloom Camp. This champion spawned with the Phase-Shifted bounty status only allowing it to be attacked during the blue ring being present. However breaking the boss's defiance bar caused the blue ring to dissapear, which made the boss evade 100% of the attacks until the bar was back up and it was able to cast the phase shift skill. Not breaking the boss defiance bar allowed us to kill it as the blue ring lasted longer, but I think this is effect should be fixed so players are able to attack when the defiance bar is broken and or have the blue rings be independant of the boss's defiance bar. https://wiki.guildwars2.com/wiki/Phase-Shifted_(bounty)