Now using the Montebello map and OoB the more unusual behaviour has diminished but not disappeared altogether.
In the screenshot Ney is under "deploy on line" orders and Grouchy is "Link in support". Grouchy's corp is highlighted in yellow.
You can see one cavalry unit well in advance of the rest. When I checked this in 3D the unit was showing "Unit Attacked" orders and seemed to have called out an opposing cavalry unit in a duel as this was the only enemy unit showing "unit attacked".