Sanctum Floor 4 Boss Bug with cannot be damaged Boon

I was running my Sanctum and got the boon cannot be damaged until the next room is completed right before the boss fight.
I play hardcore, so i tested if it really worked on the bossfight and it worked.
when the the mechanic started i manage to pick up all the sandclocks on the ground, but it seems like the last one was to late because the boss still did his run ending animation.
I wasnt really worried, because i couldnt be damaged so in my mind the worst case scenario was failing the run.
But it just killed my character.
i get along with beeing killed by bugged collossus fight in act 2 or some on death effect thats barely visible, but loosing a lvl 88 char, in a scenario where the game tells me YOU CANNOT BE DAMAGED is really bad and finally got me to the point, that i will wait for the next POE1 league and maybe play POE 2 again when it releases.

I dont want to be negative about the game,i get its beta and there is a lot of things to work on, but this death feels even worse than a dc or lag death because the game kinda lied to me.

I had this exact issue had boon could not damaged in next room took no damage until he was half way health then all of a sudden got one shot after he froze time