New flowcharts feature!
What's the difference between the new Teleport action and Set position?
'Set position' tries to change the velocity to match the position update. 'Teleport' just moves the physics body position without manipulating the velocity. It makes it easier to make 'portal' style systems (e.g. where an object is thrown in to a portal and appears out another, preserving its velocity).
The physics engine doesn't like it when you interfere from the outside, I suppose that's to allow setting the position without making box2D sad.