'01 M3 door lock problem

My 2-door 2001 M3 (USA 72k) driver's side door lock won't pop up but will pop down when using the key remote. I can hear the lock mechanism working but only rarely does the door lock button go up, unlocking the door (the passenger side door works perfectly). I've been using the key to unlock the door and this method functions properly. I think I've heard of this problem. Is this a known issue? Any advice toward fixing this is greatly appreciated.