The forcing of change of combat mode doesn't work anymore after the group has encountered an enemy group. Even if the enemy group is deleted, the opposing group would stay in combat mode. My guess is that the "awareness" of these deleted enemy group is not deleted in the groups that have recognized this enemy group. After some time (a fixed, very slow update rate?) the opposing group go into lower alert levels.
Changing combat mode by zeus before the enemy group is recognized by the opposing group would work immediately.
I understand that if the enemy group is still present, the deletion of that awareness would be not a good idea. But today it looks like a group in combat behavior would not be hear of the commands of the zeus (no move, no retreat). This should be fixed.
Here my ideas of fixing this:

• if zeus force the behavior mode to a different state, first it should be cancel the ongoing engagements. If zeus had set an move way point before, then set group to flee/retreat.
• if zeus delete an enemy group, the awareness of the ai for that deleted group should deleted/reset immediately (at least in these groups with direct engagements with that deleted group were ongoing).
• It should be investigated if it make sense that in the event of deleting a group an update of this "awareness" by the remaining groups should be triggered in general and immediately.