Reported by Square Enix on UDN,
1- open the editor
2- double click on NewBehaviorTree
3- Doubleclick on the composite node
4- Right click on empty space and add Blackboard
5- Duplicate the AND node
6- Save and close NewBehaviorTree
7- Open NewBehaviorTree
8- Break link from the Second IN of the first AND node
9- Plug the previously created Blackboard to the the first AND node
10- Save and close file
11- close the editor
12- open the editor and go back to the CompositeDecorator
13- Notice that the name (and reference) are now unset, breaking the CompositeDecorator.
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-74557 in the post.