Creating a duplicate of a Blueprint class that has an AttributeSet seems to be interfering with the creation of the AttributeSet.
1) Create a new Action RPG Sample Project from the launcher.
2)Within the Blueprints Folder->Create a Duplicate of Blueprint class of "BP_PlayerCharacter". Right click on "BP_PlayerCharacter" and select Duplicate.
3) Set the Duplicated Blueprint class "BP_PlayerCharacter1" as the Default Pawn Class for the selected GameMode in the World Settings panel.
4) Play in Editor. Press enter to pass the intro.
Results: Editor crashes. See Call Stack for full log.
Expected: Editor should continue playing the game normally as if the original "BP_PlayerCharacter" class was the Default Pawn Class
There's no existing public thread on this issue, so head over to Questions & Answers just mention UE-81109 in the post.