Doryani doesn't want to give me higher-tier stones.

Hello,

I’ve been playing the game for almost 300 hours with a single character.
I’m in the endgame.
I was progressing steadily and calmly until the latest patch.

I go see Doryani. He has level 11 stones. My understanding was this: I would enter a zone with monsters one level higher and a boss with a level 10 stone. I’d defeat the boss, and Doryani would automatically start selling me higher-tier stones — in this case, level 11.

Since the update (though maybe it's unrelated), I’ve done zones with level 12 stones (even 13), defeated the boss, and nothing happens. Doryani keeps selling level 11 stones.

I thought maybe I needed to complete a nexus of tier 7 or higher. So I struggled to find one, picked a tier 7 stone with 4 augments, defeated the boss — and still nothing. I even cleared a tier 7 nexus without dying, and still nothing.

Long story short, I feel stuck and frustrated. I don’t understand what I’m doing wrong or missing that’s preventing me from progressing and getting Doryani to offer higher-tier stones.

Could you explain what I’m doing wrong or what I should be doing instead?

Regards.

S.