The machine measures in mm.
As far ad I know, Jetrock is using the stock sled/kinematics. We have lots of
known problems with that layout (see the accuracy page on the wiki)
he will need to go to triangular kinematics at some point.
But that’s not the problem he’s having with ‘home’ moving.
That’s either a bug, a shutdown problem, or he’s somehow hitting the button to
redefine where home is without realizing it.