Wasn’t sure how to start this topic but consider it important. Many years ago I owned a ShopBot 4x8 router. Fortunately one of the first very important things I learned was that if your unit is powered down you do NOT want to move any of the carriages manually. May apply to powered up also. The reason being that the stepper motors are of course motors but they can also be generators. What does a generator do? It generates electricity. What happens to the electricity it generates? It backfeeds into your controller. This, of course, could fry your control board. Maybe Andy and/or Chris can verify and elaborate on this post. Would like to make sure this is still true so no one accidently damages their controller. I will post this on Facebook too for those that haven’t found the forum yet.
I will echo what Chris Thorog and Others said on the FB Page. The Longmill and the Mill One are bother driven with acme screws. They are not able to be shoved around like a belt driven system. Therefore the steppers cannot generate the electricity your talking about. In order to move the X axis you have to turn the screw. This is not fast enough to do anything to the boards. No damage can happen like on a belt driven system.
One more reason a screw driven system is far more superior.