In the example, I "combined" the unit at the top of the stack with the unit at the bottom. The unit at the top of the stack now shows "+++" as if it has multiple components, but it's still only a single company.
Reachable hexes calculation for a unit maintaining a bridge is incorrect. The unit can only cross its own bridge, but according to the reachable hexes it can move another hex in a line. Attempting to move to that second hex triggers the correct error message "units building or maintaining bridge cannot move away from bridge."
