Really, the patriot missiles are rather unstable, the best way to keep them stable is to keep them shutoff and use a scanner to detect particular heat signatures which come from missiles. Cross-check the event with a time-line of what is supposed to happen that day and determine if the missile is hostile or friendly. If it's hostile, switch on the patriot missile battery, manually lock on target (Making sure not to allow the missile to lock onto friendlies) and missiles away.
