Only one of the objects involved in a collision should have a polygonal hull. Do not set this flag for moving objects or for animated models.

action DNAnemy
{
my.ambient = -100;
while (player == null) {wait (1);}
my.z = player.z; // set the same height for the enemy ships and the player
var shuttle_speed;
my.skill10 = 2;
my.skill40 = 5; // I'm a ship
my.enable_impact = on;
my.event = destroy_them;
c_setminmax(me);
shuttle_speed.x = global_speed;
shuttle_speed.y = 0;
shuttle_speed.z = 0;
my.skill1 = 1 + int(random(70));
while ((my.x > -800) && (my.skill10 > 0))
{
move_mode = ignore_you + ignore_passable;
ent_move (nullvector, shuttle_speed);
my.tilt += 5*time_step;
wait (1);
}
ent_create(explosion_pcx, vector(my.x, my.y, my.z), animate_explosion);
wait(10);
ent_create(explosion_pcx, vector(my.x, (my.y + 110), my.z), animate_explosion);
ent_create(explosion_pcx, vector(my.x, (my.y - 110), my.z), animate_explosion);
ent_create(dnapart_mdl, vector(my.x, (my.y + 110), my.z), dna_part);
ent_create(dnapart_mdl, vector(my.x, (my.y - 110), my.z), dna_part);
ent_remove(me);
}