does this only happend when the car is parked, driving or both? If the light is on when you come to the X then that means it recently opened (within 5mins). If the light is alway on when you get to it and it only happeneds when the key is out of the ignition, that will narrow the problem to your remote, or a remote signal....

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Robert

1994 740iL
2001 X5 4.4i Sport
2004 Kawasaki ZX-6R
2009 VW Jetta S