I had already collected the 2 dragon eyes from the other dragon statues (don't know if this is relevant) and after finding the 3rd statue, I activated it. It gave me the quest to fetch the 2 stones, I stepped of the tile and back on and the quest continued. I fought the dragons and after they were defeated nothing happened. Only an Ashwake dragon I could not interact with remained. Clicking the quest icon selected the dragon once and allowed me to rename (?) it. Afterwards even that was impossible.