One of the quests given to you by Preston, 'Ghoul Problem at Sanctuary Hills', is broken for me.

It tells me to go to Wicked Shipping Fleet Lockup (an area I cleared near the beginning of the game) and clear out the ghouls for Sanctuary Hills. Only problem is that when I get there, only 1 or 2 ghouls spawn and the marker stays pointing inside the building. I guess I'm supposed to kill the ghouls that were originally inside, but they don't respawn.

At this point, the mission fails and I'm told to go back to Preston to report that I've failed. Even going back to Sanctuary, there is no dialogue choice for me to tell him about the apparent failure.