Hello.
Backstory:
My character is in the Legion. The civil war has not been decided. My character is also a member of the Dawnguard.
I was in the middle of The Fallen. I just finished speaking to Arngeir. After talking with him, I received a notice that I had just successfully completed a quest called A Jarl's Justice.
I had no such quest, and checked my completed quest log, and found no such quest that was grayed out. Yes, I checked every kind of quest available to me. I had to look it up to see it was a radiant quest for the Dawnguard. But my character did not do this quest.
No spoilers if possible for the Civil War (I've done the others before), but I did go to UESP to see if there were any bugs, regarding this and saw none.
I have a lot of saves, and have succesfully avoided a lot of quest bugs so far, but not all.
Is this an issue?