Oh interesting, I didn't realize that the mayor's insignia dialogue wasn't a mandatory part of the Haven quest. I'll take note of that, and thank you for discovering it. Regardless, I'm glad that you were able to complete the Haven quest, so congrats!

As for the diamond nugget quest, unfortunately yes, it's one of those events that only happens once per pet (which is either a bug or misconfiguration). However, I had an idea... I wonder what would happen if I moved your pet to the exact block ID where that Sunobra is? I wonder if your pet would still be locked out. Would you be interested in trying that? I can always move your pet back to the Entrance Gate if it doesn't work.

The next issue is, I don't know Sunobra's block ID off the top of my head. I'll have to hatch a new Techtagon and throw it in the adventure to find out, which is easy enough. Just might take a little time to grind. This is only if you'd like me to try the method above of course! Many people have had the same issue as you, so it might help future players too.