space shooter game not working fine on android device, enemy ships are automatically destroying

Game is running fine in unity engine but after building the apk file and installing it in android device, its not workin fine as it was in unity. enemy ships keep on destroying themselevs when they enter in the scene but when i removed the sphere collider of the enemy ship and then build the game then they are working fine but i am not able to kill the them because collider is not there. I am not getting where the problem is why its not working in android. please help someone.