That sounds like the latch internals are binding. There is a spring inside that moves the latch pawl and another that moves the locking pawl behind it. If dirt or rust builds up inside on the parts the latch won't lock properly and it will come open freely. What you can try is to put a screwdriver in the latch and hold the handle so you can move the latch pawl. Then spray some WD40 or similar in there then cycle the latch a few times, then spray some more and see if it flushes out any dirt and lets it work.
The other option is to remove and replace the latch assembly. To do that you remove the inner door panel by removing the screws and releasing the clips shown. Then you remove the glass from the door by lining up the two clamp bolts in the glass retainer with the removal holes. Then you loosen them and lift the glass out. Once you have the glass out you remove the door module, that is the large panel the window motor and cables are bolted to. Now you have access to remove the screws that hold the outer door handle. That will allow you to remove the latch screws and the latch. Then you reverse the process. Be careful not to scratch the glass when you R&R it. When you reinstall the glass be sure to line it up before you tighten the clamps down.
Images (Click to enlarge)
Sunday, December 15th, 2019 AT 4:28 PM