Uhm, i realize this is irrevelant but still:
At the singleplayer map where you have to arrive to defend the outpost against several orc tribes, one of the northern preplaced production structures in the human camp can occasionally unload the trained battalion into the mountain area at the moment of training completion, rendering them imprisoned within the mountain terrain, able to move around within but unable to move out. Inspecially useful for defending as enemy melee units will still try to reach the ranged battalion but cant get past the pathing blockers.
Another case of this was northernmost orc tribe having an worker spawn into an mountain, rebuilding barracks on the not-buildable normally rock terrain, then spawning troops therein that cant get out to attack.(and i was wondering why they did not attack harshly as before)
I assume this happent since you have used pathing blockers only at the edges of the terrain that is wanted to be inaccessible.