I have been using this for about 5 years with no trouble. Recently the alarm stopped responding to the arming/disarming signal from keyfobs (3) and the keypad in the hallway. There is no low battery warning on any of the devices, including the siren. However, if I stand outside just underneath the siren everything works (including the keypad, which is removable of course.) All I can think of is some sort of intereference. Any ideas, or will I be standing in the flowerbed from now onwards to arm and disarm?