Doesn't sound like a bug, you just didn't find the right spot.
At the end of the main hall there's a large room. In that room there's a stack of crates, go behind that. The hint would be that the room looks important and you have a crate disguise.
You also need at least 1 NCU free for the crate disguise. Wish it was classed as a hostile nano or something so it didn't take NCU space as my first time through that my NCU was completely full and the item to get the crate disguise was used up. So I had leave the mission area and enter again to get another set of eight mobs and start over.