I strongly believe it has something to do with the station tower. my owner's manual warns to be aware of using the wireless remote control to unlock/lock the car. it says....

"If the wireless remote control key does not actuate the doors or alarm, or operate from a normal distance or if the indicator light on the key is dimmed or does not come on:
* Check for cloeseness to a radio transmitter such as a radio station or an airport which can interfere with normal operation of the key.
..."