Theory time:
Shaka and Edison have their masks taken off: they're both the traitors, but have been hacked by Enel. Enel wants to take over all of Vegapunk's robots and wage war with the entire world using technology.
Caribou met up with Shiryu and Laffitte, told them he has information about Ancient Weapons, and wants to join Blackbeard's crew. Shiryu wants him to kill every Punk but the Stella. This is why the Cipher Pol agents didn't see who put the Stella in the cell: Shiryu was invisible.