Not receiving book with atlas passives - boss not spawning

I defeated the boss (I died once) in the corrupted nexus, but I didn't receive the book with passives, because the corrupted boss never spawned. The waystone was T14 + irradiated, and I need only T6+ boss kills to progress the quest further. The area became normally cleansed.

Also it was impossible to leave the arena after the fight. The map was Rustbowl.