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.