For anyone else, I wrestled with this problem over the weekend.
Found out that the bracket that held on my lock cylinder was cracked causing the lock to not fully change (in my case, I couldn't unlock the back glass). There is little slide at the front of the lock that pushes down on the latch rod. It rotates between two reliefs in the cylinder. One does nothing, the other allows it to unlatch the window.
Now, since the bracket was snapped at the top, the lock hung at a slight angle causing the button to get stuck and the slide to not rotate completely. I plan to eventually repair this properly, but since it involves completely disassembling the back door latch assembly to get to the two bolts that hold it on, I have decided to hold off. The way I fixed it for now was with zip ties. There is a small hole (about 3/8" to 1/2" in diameter) above the lock that does not appear to have any purpose. I looped the zip tie through that hole and around the pin coming out of the back of the cylinder and tightened it as much as I could by hand. Now my back glass locks and unlocks properly and my button doesn't get stuck (as often). Next time I take the door apart, I will try to remember to get pictures.