[jivemi]

Well Imp, what I did was go back to an earlier save when the Belgian units near the off-map VH weren't stunned by artillery and, switching sides, tried to move any of them onto the hex in question. None of them did so, since that hex was on the north (upper) off-map edge. Yet when I moved them to the western (left) off-map edge they duly exited.

Can't say what would happen if the grey-area VH is on an east-west (or right-left) map-edge, but it seems that if it's north-south (upper-lower) then it's simply inoperative since units can't exit the map that way. Here's a couple saves to demonstrate:

(Yes I'm as [more?] enthusiastic about this game as you are. Thanks for sharing your experiences and joie de vivre. Cheers!)