Hi.
I was running vanilla Skyrim on Xbox One, trying to get through the first companion quest.
I was tasked with killing the leader of the winter war ship - I arrived and slaughtered the bunch, but the quest won't progress.
The quest mark is in an empty room. Waiting for in-game days and weeks won't respawn anything. Fast-travelling back and forth won't do anything either.
I tried to mod with USSEP, but it seems you guys haven't patched this sucker.
Also googling when around, this bug seems to have existed since the original edition - https://steamcommunity.com/app/72850/discussions/0/487876568225416422/
Cheers.