Tried with GamePad and Vive Controllers, having Gamepad wire connected + 2 Vive controllers caused somewhat random behavior or sometimes only vibrating Vive's (1 or 2) and sometimes only Gamepad and sometimes all 3 at once.
Another scenario: vibrated 2 vives until game paused, at which point only the gamepad vibrated.
Create a new map + Pawn and at Begin Play inside Pawn add a ClientForceFeedback node with a custom curve (See first attached image)
Create force feedback effect (See second image) and assign to feedback node.
Result: Feedback continues to process during game paused. (Bonus: Behaves inconstantly across multiple runs)
There's no existing public thread on this issue, so head over toAnswerHub just mention UE-33773 in the post.