2000 A4 1.8T Quattro last night I was about to gave my friend a ride as he jump in the back seat, he noticed that the left back door won't close and he tried numerous time by slamming the door & the door still wouldn't lock, which I thought was no big deal. On my way back I stopped to check out what was the problem & I didn't see anywrong, no damage or acc mark anything but the door wouldn't stay close I push it myself a few times, but it's not locking. When I lock the car, the left back door won't stay lock also someone could just pull the door & get inside the car. So please help or let me know what I can do to solve that problem. By the way I'm selling the car anyone is interested let know I send u an add.