https://discussions.ubisoft.com/topic/96717/missing-one-tablet-for-excalibur/1
I am having the same problem. I believe I am missing the cauldron tablet (pillar 4) and I don't have any back up saves that show I have it. Is there a work around for this? I've checked all the caves numerous times. All of the Zealots have been eliminated. Is there anything we can do?