Just to recap my prevoius answer. It isnt a bug.
To get the last quest you got to be in the Fetid Halls. To access this area you have to get the daily quest "Noxious times" in towne from the same NPC that gives you the RadRoach boss quest.
After taking the daily quest access to Roach Motel and from there access to the Fetid Halls.
Once inside the Fetid Halls talk to the Containment unit (should have a yellow exclamation point over it).
The purpose of the quest will be to destroy all containment units in the level (8) and then go back to the initial NPC containment pod to turn in the quest.