Basically, I pretty much cleared everything I was able to in Neketaka before moving on to anything else, and the next quest chain I started was with the Pincipi.
This means I completed Eulogies of the Dead before I ever got the Symbols of Death quest, and have killed Yesyr and read all 3 tablets. I was intercepted by the ghost ship en route to neketaka, but she let me go as I was marked by Berath. However, whilst the quest log for Eulogies of the Dead indicates I read all tablets, the quest log for Symbols of Death indicates that I have read only the first 2, and the door to Yesyr's chamber is still locked.
The high priest of berath is gone now.
I have a strong suspicion that this is a bug, but has anyone else been in this situation, and is there any way to progress the quest?