ALVA and the Temple of Atzoatl Bug?

Hi GGG,

I'm a Korean player who's been enjoying Path of Exile for many years, and I’ve always loved the Incursion mechanic — especially building up the Temple of Atzoatl with Alva.

However, since the start of this league, I’ve noticed something odd:
The frequency of tier 2 room upgrades by Architects has significantly dropped. It feels much harder than before to get upgraded rooms, even when I do a large number of incursions.

I’ve checked the patch notes and didn’t see any changes related to this mechanic.
So I’m wondering:

could this be a bug?

Thanks!