I had the issue of getting a dead trigger when you rack the slide to SA. I filed down the main surface of the disconnector shown in red. I had to take off A LOT. Much more than I was expecting. Don't be afraid to file a lot off if the first you times you try and it doesn't help. I was using 80 grit sandpaper followed by 1000 to smooth it by the end. I probably disassembled, filed and reassembled about 50 times.
Thanks everyone for posting about this topic. It saved me from sending in my gun to CGW for gunsmithing!
Here's another link I found helpful: