If you really wanted them to move down so they don't mess up the medium frames with brood casings, take a queen excluder, put it on top of the deep, and shake every single frame from the medium out in front of the hive, put the medium back on top of the queen excluder without any bees in it, they will walk and fly back to the hive. When back in, they will stick around where the queen is, she will not be able to get back in the medium and eventually, once the workers get to cleaning some cells, she will start laying in the deep.