I completed the All in the Family quest and Tarquin was on the boat for the longest time. Now that I want to leave and move on, Malady says he is not on the ship, and a new waypoint called "Tarquin's Whereabouts" appeared by the graveyard (not where I originally found him to get the All in the Family quest). He still gives me the same dialogue about a few more items and I can go back to the ship, but he said that after I finished the quest when he was still on the boat earlier.

I presume he is supposed to be on the boat when I move to the next section, because I tried it and he was not on the boat anywhere. Anyone have any ideas on how I could get him back to the boat?