I just picked up a cheap 85 Camaro and it has this annoying problem where the driver's side door will lock whenever it's closed; even if latched gently. What could cause something like this? Passenger's side door is normal. No power locks just manual.

 

My first third gen used to do that. It was also a cheap 85 and I took the door apart and noticed that there was a lot of slop in the latch stuff. I kinda rigged mine up and it fixed the problem. I don't know the official way to fix it or what actually causes it. All I did was put a zip tie around the two rods in the door. You start super lose and keep tightening till it stops locking. If you go to tight it will make it hard to unlock the door. Good luck