I received a settlement quest from Preston Garvey that Tenpines Bluff requested assistance. I tried talking to the settlers there, but none where highlighted as quest targets and there was no dialogue available. I selected the quest in the Pip-Boy and clicked "Show on Map" and the target was near Sunshine Tidings Co-op by the lake. I traveled there only to find the corpse of an NPC highlighted as the quest target. There was no note on the body or anything to further the quest.
Much further back in the game I did run across settlers fighting raiders at that spot and sent them to Tenpines Bluff... Perhaps some were already dead but marked as settlers of that settlement? Is this quest permanently bugged now?