Units "Ghosting" through enemy provinces and units without engaging

Here's the scenario.

Player A - "Shared Map" with player B, and at "War" with player C

Player B - "Shared Map" with player a, at "Peace" with player C, has infantry stationary in Player A province centre.

Player C - at "War" with player A, don't know Diplo to B (presume it's "Peace"), has infantry moving across player A territory, and through the province centre with Player B infantry standing there.

Units in play - 2 infantry units (player B and C) in Player A territory.

Player B infantry stationary in ally province centre.

Player C moving across player A territory

I have an infantry unit stationed in an ally province. My unit is stationary on province centre.

An Infantry unit belonging to a 3player C at war with my Ally (player A) but at Peace with me... arrives at my infantry unit standing in my ally's province, and proceeds right through without triggering any of the actions below;

-Player C unit does not attack my unit (my unit should have automatically defended against any Enemy/Peace unit entering it's space.

-Player C unit does not capture territory of player A he's at war with... just passes through player A province without engaging in any way what so ever

Unless I'm missing something here (this is not Submarines stealthing (on 'Return Fire' stance) through enemy stacks)