Setting the resolution of PIE to 4K Ultra HD results in the new PIE window going very far out of the bounds of 4K. If you are using two monitors the PIE window will bleed over a good bit into the other monitor.
Results: The PIE window will expand far past the bounds of 4K (3840x2160)
Expected: The PIE window will fill a 4K screen and not far exceed it
Workaround: This can be fixed by just snapping the window to the top of the screen but it must be done every time you hit PIE
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-82383 in the post.