Talked with Sister Emi, got quest to pick up books she dropped on temple balcony.
Problem: could only pick up 2 of 4 books on the ground, other 2 refused to be picked up (yes, I had empty slots in inventory!). Talked to Emi and got quest reward, but was send to Mailbox because she said my inventory was full (while it was not! Had 3 empty slots). Probably not a quest bug, but an inventory bug.
We would need more information to debug this 1. Were certain slots empty? 2. Could there have been an invisible inventory item in the slot 3. Do you have bags that expand your inventory equiped 4. Was the empty slots only in the hotbar? (maybe the quest was searching for a free slot in the inventory.)