While I didn't have this issue, it's definetly a bug. The game in your case for some reason "didn't notice" you actually were on deck 12 already. That deck is on the Ark, it's not wherever the galaxy map is now pointing at.
I'm attaching a screenshot how the quest should look and when this deck 12 point should have appeared as "solved".
The only cure I can think of is reload a save before going on the ark and replay the whole mission.
Or, if you decided who will be next Asari pathfinder, try to talk to Cora on Tempest, she should open you a new quest going on Eos, maybe that solves this issue?