I am on the part to Track down your killer. I get to Yngwulf, progress through the dialogue and if I choose to let him go, he thanks me and then just stands there. He won't give me the key, quest will not progress. If I choose to attack him instead, he just stands there and won't attack. I have tried reloading, suiciding, attacking them and letting them kill me (let him go option). Always there is an arrow where I found him with the quest saying "Track down your killer."

Same! I mad a second save just to kill him to progress but that isnt the selection I want.