Note that setting the position directly is not a great way to move Bodies. This function should only be used for initial placement of Bodies, or when stuff needs to "warp" from one place to another. When you want Bodies to move, and not warp, use Body:applyImpulse or Body:setVelocity.

Also note that it is very possible to move Bodies into a collision state with another Body. This does not have catastrophic consequences, but a number of simulation cycles will be required to move the Bodies out of the collison state.