Ford Explorer door lock issue

I'm having issues with door locks on 2002 Explorer. Locks will not fully lock or unlock using remote or key pad. I can hear the lock mechanism function but doors will not lock or unlock. This issue started when temperature dropped at start of winter in 2008. I thought as temperature increased locks would start to work with remote but no such luck (this condition effect all 4 doors and the rear hatch). If actuator was bad why all five locks simultaneously?