When in Emerald Stairs there are apparently a bunch of quests that are unable to be handed in if you progress the main story.
You are given no warning about this which makes me believe it is indeed a bug.
I have to speak with Captain of the Rangers and she simply says she doesn't have time to speak with me, I was able to interact with all the other rangers just fine up until that point.
Here's to the devs fixing it, hopefully