I’ve attached a short video below, it explains everything better than words could.
https://dl.dropboxusercontent.com/u/34790815/UE4/UE4_DualAB_Setup_Bug.mp4
(It’s not limited to AnimationBlueprints, nor the editor being set to cover the entire desktop.)
System Information
Operating System: Windows 8.1 Enterprise N 64-bit (6.3, Build 9600)
BIOS: UX51VZA.204
Processor: Intel(R) Core(TM) i7-3632QM CPU @ 2.20GHz (8 CPUs), ~2.2GHz
Memory: 8192MB RAM
DirectX Version: DirectX 11
Card name: NVIDIA GeForce GT 650M