(I'll try not to spoiler anything meaningful here, but really, this is for debugging quests -- not a great place to read if you don't already know the quests...)
I just received a second <City> Slayer quest. First from king of Daggerfall, second from Prince Lhotun in Sentinel (doubt the details matter, but just in case...) The first quest went normally. The second one was a little odd. I strongly suspect that a quest state variable didn't get cleared either at the end of the first quest or the beginning of the second (I'm not familiar with how quest state variables are managed)
Detailed experience of the second quest:
- Normal until I got to the "associate" who actually knows what's going on.
- First time I talked to her, she thanked me for killing the slayer using his name (which had not been mentioned yet, and whom I had not killed). Gives me a wand as reward. Oddly, places it directly into my inventory instead of the trade dialog I'm used to getting in these situations, but I'm assuming that's a detail of the quest script.
- Talk to her again immediately after, and she gives the expected response, and sends you to the next step of the quest.
- Go see the third individual, they give me a residence to check out as normal.
- Asking around gets the residence marked on my map, as normal.
- Going into the residence, no target (slightly odd because it's a split level residence with no passage between the floors -- doubt that matters, but just in case). Go into the other half, no target.
- Look at my map, and the name of the residence is gone (normally seems to indicate quest is over)
- Check log notes, quest still appears to be active.
- Futz around trying to trigger something, including visiting at different times of day, just in case. Finally give up.
- Go see Lhotun, he thanks me, quest finished.