Before I received the quest Mapping the Archipelago: West Wakara Reef from Sanza in Neketaka I've explored the whole southwestern quadrant.
And now this quest is stuck and will probably remain open till doomsday.
I have only an quest entry update:
Upon a desert island, I found a Huana ruin, filled with deadly traps.
The second entry (about jungle overgrown island) is not in the journal.
EDIT:
Sorry, false alarm.
I didn't enter and explore Ruins of Amira's Roost previously, don't ask me how I just didn't.
No bug. Sorry again.