i experienced the exact same issue as you did on Windows 10.
As for you, the bug does not occur for me for new organ guns fresh from the artillery foundry. In this state, the icons for the two artillery states (firong, moving) are still both visible.
As soon as at least organ gun from the selected group switched to the firing mode, the bug affects all organ guns in the selected group. The icon for the moving state is no longer visible.
The small steps you mentioned, i found out being exactly the width of the screen. As soon as all currently selected organ guns are within the current view, they can be moved to any point on the screen (excluding a point on the minimap).
The bug does not affect other units in the selected group with mixed units, only organ guns. The non-bugged units leave the organ guns behind.