2000 LeSabre Interior Lighting Problem

I own a 2000 Buick Lesabre Custom. It just developed a problem. The interior lights stay on whether the engine is on or off. Normally, when you open a door the interior/courtesy lights stay on until you put the key in the ignition, then it goes off. It now stays on. By interior lights, I mean the overhead lamp (dual) and the lights in the front and rear door panels. Nothing on the dash remains lit and I don't get a problem showing up on the instrument panel. The lights go off after the 10 battery saver timer. I recently had a problem with a rear door window power window (which is disconnected while waiting on parts). What could be causing this problem?

Not sure if this will help any but I have a 1997 that the interior lights blinked all night.

I tore out the keyless entry, bought a new BCM (Body Control Module), payed to have a guy tell me it's not the door latch.

I finally traced it back to the switch. The one that turns the interior lights on, and has a dimmer.

I unplugged it and it stopped blinking.

I never had to get a switch because I took it apart and cleaned it. I haven't had the problem again.

Hope I can say anything that can help you at all. I would start with the light switch.
Chris.