I’ve killed her a few times this season already. I only started having this issue after this most recent patch, she has become immune to damage in phase 1. This has happened two separate times. I can take her down to the last part of phase 1, then can never damage her again. I took her to every part of the map and tried damaging her, nothing. This was on Hardcore.
i’ve run into this issue also in group play(in full 4 person party)
in my experience, she only bugs out in phase 1(in t1-t4) when you start the fight with 4 people in the party, but if you start the fight with 3 people, and then someone joins, she doesnt get bugged at 40% health.
seems like the issue is starting the fight in full party
never had the issue solo or with 2 other people in the party