I have a 2001 Outback. About 1 out of 10 times when I unlock the doors with the remote control the rear lift gate door remains locked. I'm unable to unlock it with the key. I can hear it trying to open but it doesn't. Normally if I wait a period of time and repeatedly lock and unlock the doors, eventually it unlocks. Then it works fine for awhile, and then the problem starts again. Is this a lubrication issue?