Ancestral Vault - Can not find Copperbeard puzzle

pixel_player85989719

This is crazy, I swear I have opened everything and been down every hole I can not find how to enter Copperbeard so I can put the stones in place, I have done the other 5, used the toothpick opened and collected from all vaults but for the life of me I can't find Copperbeard and it's seriously doing my head in, I'm at 620/643 I even tried loggin into laptop when normally use phone to see if I culd see whole map to find the missing entrance! Help me pleaseeeeeee I searched the forum feel like I've read a million posts and everyone just says the shield is in Copperbeard LOL I know that, I have the combo but losing my mind LOL

red_herring

pixel_player85989719

In the middle image, in the middle on the left, look for the staircase marked D. I believe the stone puzzles only require 3 stones, but for some reason this map shows 4.