Boss skill points not granted

I cannot get my last tree points for Boss tree.

I have 8 points spent, including 2 from Arbiter. I did 2 attempts:
1. T16 + boss + corruption + irradiate + +4 boss difficulty on atlas boss tree
2. T16 + boss + corruption + irradiate + +5 boss difficulty on atlas boss tree

In both cases I did not get my last tree points.

Are there any requirements regarding waystone except being T16? Or maybe I need to fight with Arbiter again?

UPDATE
I will be testing 2 cases:
- I will remove 2 points from Arbiter tree
- I will check that when I enter a map the Area Level is 82, I guess in my cases it was 81

UPDATE 2
Apparently I don't know how to read. It has to be:
- T16 - master level is 80 then
- irradiated (or in my case not because of Organized Forces) + 1 Monster Level of Area
- corrupted or cleansed map WITH MOD +1 Monster Level of Area - THIS IS WHAT I WAS MISSING, not all corrupted/cleansed map has this mod
Only then we have 82 Area Level.