Minor spoilers ahead. This is the quest where Drithnil Virith sends the player to ask Nisirel why she has been "snooping" around his shop. Nisirel has fallen in love with Drithnil. If the player confronts Nisirel directly, she gets upset and asks the player to leave. But if the player checks Nisirel's diary upstairs, they can report the truth to Drithnil for a good resolution.

Bug #1: It's possible to never actually confront Nisirel, but just look around, check her diary, and report back to Drithnil. If the player does that, everyone's dialog after the quest is resolved still reads as if the player told Nisirel of Drithnil's accusations. See screenshot for an example.

Bug #2: Once the quest is completed, Drithnil still greets the player with a request to talk to Nisirel, as if the quest hasn't been done yet. See the second screenshot.