Back saving to 18.x or 22.x is unstable

I have a client who asked for an 18.x version of the file I was working. I built the file in 23.1 so I backsaved a version for him. The problem he and I found was that weird anomolies begin showing up. Specifically, when I add a null and try to move a group of layers, they don't move with the null. You can see the outline of the shape layer in its new position, but you can't actually see the change until you close AE and open it back up again.