Unless there's something I'm not aware of or have a misunderstanding about, there seems to be a fairly major isolation bug.
Using the Schlieffen Plan, I played the right of passage event against Belgium. I checked Belgium's diplomacy and right of passage was given to the CP. Also, the right of passage card said that supply would be traced through Belgium for 6 turns.
I moved the 1st army past Liege and into Belgium. I move the 3rd army to the north (left on the map) of Luxembourg, next to the locked 4th army in Luxumbourg.
The next turn both the 1st and 3rd army came up isolated. It seems that the game is not taking into account right of passage when determining isolation, since Beligum and Luxembourg were the "owner's" of the regions surrounding the 1st and 3rd.