Yellow harvest boss bugged

Hi, yellow boss from harvest is bugged. When it drops to ~60% HP it's just stuck in normal form and is invincible for random amount of time. Sometimes it just jump around and never phases, sometimes it phases after 5-10 seconds. Other bosses behaves normally.

Kind Regards

+1 the random time for me is 2-3 min, he stick in his immune phase...I doubt its design like this...

I have encountered this issue as well at least a couple of times