Radio doesn't shut off when door opens

2004 Chev Malibu - Radio doesn't always shut off when car is off, key removed, and door opened.
So far I've shut door, and opened it again. Usually remedies the situation, but I've noticed that I've had to almost slam the door.
Is there some contact spot I could clean? Or is it a loose wire? I don't have a whole lot of money to spend, but I don't want to miss it and have a dead battery either.
I did have to replace the circit board a few years ago.

Thanks!