Door only locks from the inside
I'm having a strange issue with my driver's side door. The door is a 1985 with a roll-up window and lift-up handle. The door can be unlocked from the outside just fine, as well as from the inside by pulling up on the lock. When I lock it from the outside, however, the key turns just like it had locked, but the handle still opens the door. The only way to get the door secured is to use the key in the door to "lock it" from the outside, knowing it isn't actually locked YET, and then push the lock down from the inside. ONLY THEN, is it actually locked and secure.
Has anyone else had this issue? Looking around the door locks and mechanisms, everything appears to be okay but I need to dig deeper and not quite sure where to look.