I marked the extra tasks for the tree → “Conquer a stronghold”
I conquered all strongholds in fractured peaks → still blocked according to the icons and the info text that is shown for the active task
I conquered all strongholds → still blocked…
I just did a task (kill beast in the ice?) → I received the points for the tree.
So only the UI is not up 2 date? 
(But the UI is always wrong?)