During Yris's quest you need to use a specific potion... however, it only works if you left it at home, if you actually thought ahead and took the potion with you in your backpack, then it won't be detected by the game and won't be available for use in her quest.
Viewing post in Old Bug Report Thread
Ikr? Kinda funny to think of how it actually happens.
Yris: Just a sec, let me get ready (heads to other room)
Player: Ok, time to...Crap! I forgot it! *quickly dashes out to the portal, heads home, grabs potion, heads back through portal, into tavern, to the back room, uses potion, and relaxes just in time for Yris to walk out* You ready?
Yris: Yeah!...Why do you look so sweaty? You nervous~?
Player: Uh....yeah...let's go with that.