MightyGood

I had the same kind of problem with an animation recently. As long as you set up the Idle as a Property in the script you don't need the SendAnimationEvent(), just the Actor.PlayIdle(IdleBedSleeping)

Are you moving just the mannequins or are you also moving the Mannequin Activator? A mannequin has three parts: the NPC model, the Activator, and the XDirectionMarker. The NPC is the physical model, the activator is the thing you interact with, the Marker is a one-pointed path that makes the mannequins stand still. I would guess you are only moving the physical model and leaving the activator behind. Turn Markers on in the creation kit (press "M" while the render window is in focus) and make sure you grab the orangy boxes that the mannequin is in as well as the mannequin form as well.