Strange, tried it again on a newer save making my way there in a hurry. I thought maybe me doing the gray boulder puzzle first was breaking it. But I tried doing the brown one first and it didn't play an event that gave me the key either. I'll link you my save file so that you could review it my issue more closely. Thanks again for being really responsive. It makes me feel happy that you look into these issues quickly :D.
https://drive.google.com/file/d/1MVPmU6hZvxuyJ0OrJVTcXUsQLbpRHEN-/view?usp=shari...
Let me send you that as well.
https://drive.google.com/file/d/1gXENmUBwpYbRJPuXeu7ttgVBrs-5sezK/view?usp=shari...
Included my Config just in case that was needed as well.
