I recently found a refugee center and started the “kill all zombiest in X wing”, it was pretty easy but when i returned to the trader the mission is still incompleted. No windows broken, no stuck in place zombies i killed them all.
The named shocker zombie has to be killed and either [s]mashed or [B]utchered.
Also sometimes the main guy wanders outside the refugee center, but the named shocker zombie is the important one.
I dunno if they fixed the center itself either. Sometimes the NPCs get stuffed in the walls and tossed outside on the street. So if NPCs are all over the place in strange places this could part of the problem as well.