I used the physics collision trigger and behaviors start unexpectedly

First, remember that the physics collision trigger uses the bounding boxes of each physicalized limb to compute the collision, so it may starts behavior when characters are not exactly colliding but are very close.

However another frequent reason for a physics collision trigger unexpectedly starting is that if the crowd is dense and a lot of characters are already in Kinematic mode, they may be colliding a bit with each others. However you do not want all your soldiers to fall down each time they touch each others' pinky! That's why a filter has been added on the Physics Collision Trigger.

Usually what you want is to start your behavior when a kinematic mode character (walking soldier) is hit by a dynamic mode one (arrow, other soldier flying in the air...). In this case use the "collide with dynamic mode entities" filter on your Physics Collision Trigger.