To answer your question: each Part is independent of others. So you can change the location of a Group without changing the location of its member nodes. And vice-versa. That is what it appears has happened – something set the location of the “Logical Modelll” group without setting the locations of its member nodes. Or vice-versa.
If you want to move a group including its members, call the Part.move or Part.moveTo method. All Layouts should call move or moveTo, for example, just in case the Nodes that they are laying out happen to be Groups.
I cannot tell what your app is doing, but I would guess that the Binding on the Group.position is being given inconsistent point data from the positions of its member Nodes. Look at your model data carefully.