My garage door has been working fine up until last week. It will not work (for the most part) when I am outside. If I am inside it works fine. Som etimes it will work if I am standing right outside the door. I have replac ed the battery in both remotes and reprogramed them. Still nothing. The o utside keypad works and the inside one too. It is a 3 yr old liftmaster. Anyone have any ideas before I make the appointment for a service call?