Getting Units to keep attacking in a 'tech wars' like map

Level 7
Jul 25, 2006
My map is kinda like a tech wars map you make a building that spawns units but the units are given to a neutral player (victim and extra) and are sent orders by triggers. I order my units to attack to specific areas and they seem to stay and fight other units no problem but when they come to towers on ledges like the one below in the picture, they will attack the tower for about 3 seconds then run away (move order string) to the point they spawned from before the tower is even dead even while the tower is attacking them, it doesnt make any sense. :

I modified gameplay constants like guard distance, guard return time, guard return distance
and unit properties such as priority, acquisition range, can flee. Still the units run away from towers after attacking them for a short time. I really dont understand why. Any ideas?