Issue #21954: Forbidden Legend Quest-line Glitch
During a play through I managed to accidentally glitch and break the Forbidden Legend Quest line. I presume during the step between "Investigate the Gauldur Legend" and "Learn the truth from Daynas Valen". The "Investigate the Gauldur Legend step requires you to find Daynas Valen's notes, and the step "Learn the Truth from Daynas Valen" requires you to find his body and pick up quest items from the body (Ivory Dragon Claw, and his notes).
Here's the problem:
As I was oblivious to the mission since I did not have it equipped, I went through the mission area (Folgunthur) missing the notes, but I picked up the claw from Daynas Valen's Body (which was obviously part of step 2) and cleared out the dungeon. When I decided to finally start the quest I found the notes I had missed and then I had to investigate Valen's body and pick up the claw, to which I had already done.. so the mission still wants me to pick up the claw from his body.. I also can't drop the claw because it's a quest item. So now the quest is broken with a marker leading to Valen's Empty Body.
Maybe I was stupid but I've realised this could be broken without even starting the questline..