You can try this:
(Changed code:)


action slave
{
var slave_target;
VECTOR slave_speed;

my.passable = on;
while (robot_boss == null) {wait (1);}
while (1)
{
my.tilt = 0;
slave_target.x = robot_boss.x; // stay 50 quants
slave_target.y = robot_boss.y; // behind robot_boss
slave_target.z = robot_boss.z;


vec_set (temp.x, slave_target.x);
vec_sub (temp.x, my.x);
vec_to_angle (my.skill30, temp);

slave_speed.x = 12*time_step;
vec_rotate(slave_speed.x,my.skill30);

ent_move (nullvector,slave_speed);

my.tilt = 0;
wait (1);
}
}


I have no time to try this out now, just give it a try.