Buick Repair Questions? Ask a Mechanic for Answers ASAP
What happens is that the pivot point that presses on the lever for the latch breaks off on the handle. If you have the child lock engaged on the rear doors, i will not allow you to open the door from inside, but the outer handle is broken.
You will need to replace the handle, and it will need to be painted body color, so I would get the part first and have it painted before disassembly.
You will then have to remove the inner door trim panel in order to access the inside of the door, and pull on the rod that normally connects to the outside handle in order to open the door- then you can remove the three 10mm head screws that hold the handle on, install the new one, and connect the rod to the new handle.
Sadly, I've had a customer come in with one handle broken on 4 different occasions over the last year- so now they have 4 new handles!